Aiden I feel ya on everything you've said bro.
I'm having quite a difficult time with this bathroom dilemma myself. Here at school I'm still a "girl" but I get the odd looks and hushed whispers when I step into a women's room. Then I present as male somewhere (like a club meeting) and I get nervous about which bathroom to use, then cower and dive into the women's room, do my business and rush out, hoping no one saw me. If I ever visited my dad at work here on campus, I'd get freaked about which bathroom to use cause most of the people in his department are men and they all know me as his "daughter." So I'd be kinda screwed if I ran into one of them in the bathroom.
At work (library) I used to pace back and forth between the two restrooms before a couple of times, I dove into the men's room and no one was in there

Thankfully I work in the stacks...And so far the stacks are the ONLY place on the entire campus I've ever found a unisex bathroom. There's nowhere else here.....
So I definitely use men's rooms when out in public places (malls, restaurants) with my friends. I never get any weird looks as far as I know, because like Jay said I go into ignore mode. Here at univ though it's still confusing for me.... Maybe I'll just take Jay's inspiring advice and use the bathroom that is rightfully mine!
Also, on the note of STPs....that is EXACTLY why I got one. I got so irritated when my biomale friend said "but I sit to pee all the time." WELL GOOD FOR YOU I never had the choice. Now that I do, I'm going to use it all I want. Using my STP makes me extremely happy, sitting to pee just irritates the living hell out of me. Psychological? Maybe. I don't care. Do what you do bro.