wearing girl clothes is something many little boys do, before they're told that boys aren't supposed to wear them. they aren't even supposed to want to wear them. though that's only true in modern society, only a few decades ago, and even still in some families, the boys would wear the same practical dresses as girls would, and they'd only change into knickers when they started school. before that, gender was totally unimportant.
but worrying about gender as you grow older, is more common among transgender people. it is completely normal both for non-hetero and trans people. probably a part of the long process that it is to find your own identity when you can't identify properly with the large cis-hetero male or female group which most people in the world identify so closely with that the thought they might be something else doesn't even hit them.
wondering if you might be trans doesn't make you trans. either you are, or you're not, and there are other things that can trigger a wish to be the opposite sex or to wear clothing designed for the opposite sex. and gender typical interests aren't really that typical, so just try to pull all those out of the equation when thinking about things. it can be very tricky to find out whether you are or not. some hope they're not, but become happier for every little change they make, until all they can do is capitulate to their internal gender so they can get some peace and real happiness. others are sure that they are, but find out through the process of transition that they were really something else. there is no rule that you must have always known in order for it to be true.
i'm probably just confusing you even more right now, huh... but i really just want you to relax a little while exploring things. a full transition isn't something that every trans person needs, and some don't even want it. in order to find out what's best for you, it's very important to listen to your gut feeling, and remember those moments when you feel really good or awful about something in your interaction with other people. did the feeling stem from being treated like a specific gender? if it does, that's a rather important sign, and much more so than wanting to wear pretty dresses. it should be fairly normal for anyone to want to wear pretty dresses, as they are pretty.
sorry, i just don't really understand this gender thing at all these days.