Should I be worried, or is it all innocent?

He sounds like he is a borderline pedophile. I don't know why you are allowed to drink at 15 and if you are on medication it seems you shouldn't be drinking at all. There are some missing pieces to the story it seems. Bottom line thought, he is definitely NOT acting like an Uncle if he is on top of you while you are sleeping and holding your hand. This a big red flag and your Mom needs to wake up and realize this guy is dangerous. Stay away from him and don't go anywhere alone with him!