This may come out as a rant but I've checked like 10 shops and couldn't find a girl shirt that fits well. Most are too tight under the arms (even the xl's) and loose around tummy and waist. I normally wear a men's medium (which is kinda loose at the armpits)  but...Sweet Jesus...why is it so hard to find a shirt....

I know my upper body type is not really female but it's not of a typical male (wide chest, thin otherwise, not really muscle around chest...). Only one I found that was ~ok under my arms but too loose everywear else.

There has to be some shirts that fit me but it's like impossible. I don't even want to think how I will find clothes to fit me if I start hormones one day.

I have found the same problem with many brands. I have found that, for me, Columbia works. Joe Fresh also work and they are much cheaper. The tee shirts are nice as well. I don't know where you are but in the States, I purchased Joe Fresh clothing at J C Penny's. I also found that the 'camp' style shirts fit well. I am not big, medium in my past, and now am a large in button up tops and XL in tees.

Just tailor your own. That's what I'm doing. Bonus points if you happen to own a sewing machine, but a simple backstitch or similar is easy and I bought the needles and threads to do it for a few bucks. Now, I just sit down in front of a DVD or something and slowly convert my current shirts to perfect-fitting girl shirts.

What stores do you shop at?

I have the same issue and finding clothes is a pain. I'm really skinny, so I need like size 0 or 2 pants, but my shoulders are still broad enough that I need bigger size shirts which fit loose and aren't as clingy as I'd like. Then I have to deal with shirts potentially shrinking and since I'm about 5'9" it makes shirts almost unwearable.

I have found Rue 21 to be really nice, but you have to like juniors clothing. The clothes are cheap enough though that you don't have to worry so much about clothes lasting for the long run.

Also, raglan shirts and tunics are very nice and easy to find that fit and they're very cute. Most of my wardrobe right now consists of these kinds of clothes.

Finally I bought this one http://www.bershka.com/gb/en/woman/bershka/t--shirts/girl-c234504p5614508.html. Fits ~ok ish (but looks girly obviously). At least the large one is comfortable under the arms without being extremely baggy elsewhere.

edit: actually it's a bit baggy. In a sense that it doesn't wrap around the waist (it's more of a straight line) but it's not too bad. For the rest of my torso I would need a medium but for arms large heh.

Ok....more ranting (sorry)...Today I spent 5 hours going from shop to shop trying tshirts and I didn't find one that fit me adequately (again there were only a couple size L that fit ok at the arms/ shoulders but too loose around waist etc). I searched a mall, Zara, H&M, Bershka stores to no avail.

Yeah I searched in womens only article's floors (they are separate), but I had to use the men's fitting rooms, which meant going up 2 floors...at least I'm partially over the phobia of getting into women's departments and checking the clothes - at first I had all these salepersons telling me "these are women's" (yeah I know darn it, do you think I would get mixed up!). 

I hate my shoulders. They are skinny but still can't fit shirts. Well there are a couple of stores I haven't tried but I doubt if I'll find anything to fit me modestly.  (so much for having a slim body...eh. Funnily enough the only skinny jeans that fit me ok-ish are women's).

I feel your pain. I can't fit into any guys clothes since I'm unbelievably shrimpy () and it's pretty much the worst feeling. ((hugs))

I find Hanes women's long sleeve t's in medium work fine for me. I've fairly slender, but 5' 11" tall. My arms are a bit long for them, but I always pull them up close to my elbows anyway. Hanes has a nice clearance store on eBay with discounts and free shipping.

I also like the hanes long sleeve. Walmart had them on sale for $3 each. I bought like 6, different colors. Medium fits PERFECT.

My upper body is 42" shoulders, 38" bust, 32 underbust, 28" waist.