WHAT BATHROOM DO I USE (also how do i not get busted as ftm)

I can pass as a man AND a women, i would say i lok fairly androgonous, but more on the masculine side, anyways im going to a diff school and my mom said i could change my name/pronouns there since i do pass as a guy, i have gone into the mens washroom once or twice and i passed perfectly fine, BUTTT the issue is that in the new school theres a few kids (boys) from my grade also transferring there, idk if they are transphobic or not but i dont wanna make em uncomfy by going into the mens washroom if they see me its gonna be super awkward and i cant go itno womens bc well the girls there will prolly think im a cis guy or smth (im in middle school btw) and im not sure if they have those gender neatrul one stalls that are simulair to staff bathrooms and sometimes you gotta pee like right then and now so ive got no clue which to use if thats the case, also sometimes people do think m a girla t first its really a gamble but if i correct em they do believe that im just a feminine guy and for the second part since this is a middle school n kids are fucking cruel most peple are chill though im still fucking horrified of people finding out im trans only a few peolple know and its just my closest friends/family and this girl im friends with kinda whos going to the school to so how do i NOT get clocked as ftm i really really want people to think im a cis guy but im scared of them finding out so how do i yk have them not find out i cant go on testostorone bc thats banned for people under 16 where i live and my voice sounds pretty feminine (i do plan on trying that thing where you kind of make it sound depper by training it i forgot what its called though) also i am over the age of thirteen so dont report this or smth