This sounds like what a lot of people struggle with in their teenage years. You're at that point in life where a lot of doors open and you're trying to find yourself. Also, you could work on your self confidence, because that's a lot of the reason people change who they are around others. They feel that the person they are isn't going to meet approval. I'd say you're experiencing a bit of both of these things, but a lot of it sounds only natural, at least to me.