I am gay or not? What to do?

Wanting to wear tights does not make you gay. People telling you that you are gay does not make you gay. Even getting erections when showering in the presence of other boys does not make you gay, after all I know teenage guys that would get turned on by a tree with a hole in it. You have to ask yourself if you are attracted either sexually or emotionally to men or women. If it's only men then you are gay. If it's only women then you are straight. If it's both then you might be bisexual (attracted to men and women), polysexual (attracted to men women and certain groups of people who identify as neither such as genderqueers and intersexed people but not all groups of people outside of the gender binary) or pansexual (attracted to people regardless of gender or sex). But you are still a teenager so I wouldn't worry too much about it. This is a time for experimenting so you don't need to stick yourself with a label until you're completely sure.