i think its weird tbh… stick to ur own undergarments… ur a man. dont get caught up in all that cross dressing shizzle from now man=/ you'll get labelled as a weirdo if people find out u dont want that. sorry if i come across as harsh, but just try to put it aside. if u claim ur straight, ensure that ur behaviour matches that status.
I've known tons of guys who like wearing some type of womens clothing, and most are completely straight. A few were bi, but the majority were into women. They just felt the compulsion to exhibit some form of inner female, through feminine attire. Have fun and enjoy yourself, but be cautious, as not everyone is as open minded, and some can be downright cruel, especially at your young age.
I would recommend that you stop this imediatley. You're a man, dress like one. Also, I'm almost certain the majority of girls will respond negatively to your odd habit. Most the guys will either avoid you like the plague, or harass you (assuming they find out). Try wearing boxer briefs and a tank top under your clothes, maybe a muscle shirt. Those options are a better for a guy.