After re-reading one of your replies, one thought came to my mind. You said that you were "absolutely terrified" of going to a shop and buy woman's clothes. Well, I used to be like that as well, and it was years until I bought a dress on a shop on my own, and still, I did it during the winter holiday season, when it's "usual" for males to buy clothes for their GFs or partners. I would not even have courage to buy makeup on a supermarket...
Many, many years later I started doing a small trick — buying some male things for myself and slipping a few female ones. That allowed me to build some confidence in buying things on physical shops. This is far easier on a supermarket which also carries makeup and clothes — I could just lump it all together. Some larger supermarkets even have these self-checkout machines, so I would not even need to feel the eyes of the cash register person on me; and by carefully choosing shopping hours (e. g. during dinner hours) I would have few eyes on me. But I think it was well over a decade until I managed to get the courage to enter the women's section and just select some clothes for me; and another two years when I bought a pair of shoes, since, wearing large shoe sizes, it was more than clear that I was buying them for myself. On that occasion I even managed to get a very nice assistant to give me some tips! She clearly couldn't care less about what I was buying, she just wanted to make a sale, and was very nice.
Even today I still get nervous when shopping for myself, although I don't enter in a panic, and am even able to enjoy the whole procedure of browsing through racks until I find something I like — which is ironic, since, as a male, I utterly hate to shop for clothes (and actually haven't bought anything male in a decade: I rely on gifts from family and friends to provide me with clothes, since, to be honest, there is nothing in the male section that I find interesting...).
There was only one curious incident once. I went into a supermarket to buy some cosmetics but also bread, butter, and a few other things; but the majority of the items were makeup. The nice lady at the cash register began to scan all those items, and, at some point, she smiled but not in a malicious way, and said to me something like: "Oh, it's curious, the other day I was watching a show on TV where they talked about men who like to wear women's clothing. I always wondered where they would buy their things, the show didn't say. My apologies, this just came to my mind." I remember maintaining a smile, even though I was terrified at the moment, and said: "Really? That's very interesting! A pity I have no TV, I haven't seen that show" or something to the effect (yes, I tend to talk to everybody I see...). But afterwards I just thought: so what? 🙂 It's not as if that person was taking pictures of me and posting them on Facebook saying "Caught a crossdresser buying cosmetics at my supermarket! Watch this!" :-)
In fact, the more I talk to CDs who regularly shop pretty much everywhere, the more they tell me precisely the same: shop attendants don't care. You are a customer; they are there to make sure you have a nice shopping experience. Whoever runs a shop discriminating this or that kind of customer will quickly go out of business; shops will make sure they please everybody, and treat them as well as possible, to make sure the clients return. I had excellent service when going to two cosmetics shop to buy foundation, which is something rather hard to do by mail order unless you have experience with a certain brand — you really need to match the colour of your skin, and it's almost impossible to do so from pictures. When asking for opaque, concealing foundation, it's more than clear for the shop assistant that it is meant for me; and of course I have to try it out first, and ask advice about what works best for my skin type & colour. So in those cases it really means to enter a shop and ask to try things out first. Obviously the shop reps don't care who is buying their products.
I personally found that it helps if you are extra polite, smile a lot, but act naturally as a male, specially with female sales reps. This will make them more at ease, because I can understand that some people might not be able to react properly when asked by a male to see female items. If they're at ease, they can engage in their usual sales talk to the best of their ability, and you will benefit from a better service. On two bra-fitting services I know (I'm a happy customer of one of them), they have absolutely no problem in having a clearly male person setting an appointment and they will be aware that you will come with a pair of breast prosthesis for the fitting session. Telling them that in advance will make them much more comfortable, although, to be honest, they're far more used to these "special requests" that we tend to believe.
I'm ranting again, I do apologise... my point is actually two-fold. First to let you know that there is no reason for you to feel terrified about the experience, you're just being a good customer. A few shops I know actually love crossdressers: in general, when they're treated right, they're good, returning customers, very faithful to a specific shop or brand with whom they had a good experience. The rest of the shops simply won't care, except to the extent that they want to make a sale, and will go through pains to guarantee that you get all the help you need and are positively impressed with their service. I have yet to find a crossdresser who had a bad shopping experience!
The other is that I would like to encourage you to think a bit more about your options. If you're terrified of shopping at this stage, but are considering HRT, how will you react when your body will start changing subtly in many ways, and you will be exposed to the public (at work, with friends) with those changes? Let me give you the simplest example. After perhaps a few months, even the least breast development (which in some cases might be slightly painful or at least itchy...) will require you wearing a bra, even if it's an AA bra with no padding and no underwires; they're never completely invisible beneath your clothes. If you live in a harsh, cold climate, and need to wear thick clothing all the time, you should be fine, but... if not, even very loose T-shirts will, sooner or later, "give away" that you're wearing a bra beneath it. Forget about summer vacations on a beach (or at the swimming pool); at the very least, even if there is not much growth in terms of cup size, they will be differently shaped, have unusually-looking nipples (for a male), and you will attract undue attention which is impossible to explain. So you will really, really need to be very comfortable about all that — and if at this point you can't bear the thought of shopping for women's clothes, how will you feel when your body changes, even if just subtly?
I would only recommend you to get slowly used to the idea. Wearing panties all the time, for instance, is completely safe; nobody will notice. In most cases, you will be able to wear stockings or hoses without anyone knowing, either. You can start wearing a plain, smooth bra during the winter season, or at least when you're wearing a jacket on top, just to have a feeling on what you can expect. From my personal experience, during the winter, I can even wear a bra without my wife knowing (and she is well aware that I crossdress, and allows me to do it at home, within limits), but it's impossible to do so during the summer. During a few long trips in winter when I have to drive for many hours, but expect to stop frequently to rest, I have often worn my full set of padding — a bra with breastforms, a corset, hip & buttock padding, stockings, suspenders and a belt. While that completely re-shapes my figure to something noticeably feminine, even if I wear loose male clothing on top of it, the whole ensemble is easily disguised with a long, thick, straight overcoat. But I'm perfectly aware that I wouldn't be able to pull it off except in deep winter. So maybe you can start doing something similar just to get used to the idea and see how you feel about it; using "prosthetics" at this stage means that you can still decide when to look as shapely as a woman and when not; because, after hormones set in, you will have no more choice but to expose yourself and your new body to everyone, and you'll have to be able to deal with that.
