Well I'm a month on T but before then and now, I'm ALWAYS mistaken as a 14-16 y/o boy (so at least I pass) and I'm 19. Trying to buy E-Cig juice is sometimes hell and when I was in college "oh, you're PSEO or CIS?" (no, I'm a student -_-). I'm also 5'6, so I'm really short for a black guy which doesn't help in my case.
I am always told that I'll like it when I'm older but for now, it's a pain in the ass. And even though I'm on T, I highly doubt I'll grow a beard. My dads side, the side I take after more, are hairless beings. The men are very lucky to actually have a full goatee. Most they get is upper lip hair, my dad included. He grows a bit of stubble though. My moms side, on the other hand, are hairy. So I'm hoping my moms side kicks in with facial hair. Not for looking older, but because I like beards.
When driving I get the weirdest looks. Probably because 1) The car is designed odd and kind of long. So unless it's pushed all the way up and the seats raised some, I have issues reaching the gas and brake pedals, and 2) I look young so it's odd seeing a 14-16 y/o looking guy driving by himself on the interstate.
It was kinda funny working at the bar I used to work out. I looked too young to be working there and got asked my age three times daily by non-regulars. They would lucky think that I had to be at least 18 to work there, but some thought my 18th birthday was coming up within 6mos, so they could hire me (that one had me rolling).
The only advice I can give is to, unfortunately in your case, get used to it. I'm in your shoes and can't help it. The bright side, if you're on the small side, you can save money on clothes by buying childrens sizes! It's kinda annoying and gets on your nerves, but it's life.
Now I will say, dating wise, I get you. I'm bi, so male or female, it's hell. I'm shorter than most girls and many guys on campus look their age, and I don't fit either. I'm not the most muscular guy on earth and if my hair isn't cut wave length 24/7, I look young.
I just say be you as well. No use hiding who you are to fit other peoples perception of a trans guy, or what people think is normal. I am just now being open about my sexuality, after it being pounded into my head for years that black men are not gay or bi. Period. I can be a straight trans man but no way in hell would I be bi or gay. At that point my moms side chimes in asking why I just don't stay female then -_-... But either way I'm being open about myself and my sexuality and feel happier, to be honest. Besides, at the end of the day you're the one being you. No use being unhappy with yourself to make other people comfortable or to avoid confusing people!