Am I leading a double life? Is this bad?

Most people I hang out with at school are very innocent and don't experience a lot of typical high school things like parties and dating. I feel that life should be a good mixture of hard work and fun, and I want to live my youth to its fullest while it's still here! During conversations with clmates I feel that due to my reputation I have to censor what I say, including my experiences, or they will judge me harshly and maybe even think I am showing off. I shouldn't care what my peers think, especially in high school, but what I do is subconscious. I feel that school is a place to learn: I take difficult cles so most of the people I meet are kind of nerdy (in a good way!), but I'm not very attached to people there. I keep a very low profile which limits my relationships with others and causes me to come off as shy and reserved. Sometimes I feel like I'm leading a double life...is this wrong? Also, I will be a senior next year...is it too late to change my reputation, or is it best to leave it as it is?