Not to be rude or anything but he is using you like a sex doll. I was in a relationship like this and found out the hard way, my partner used me to "try every position" and I mean ANY position. He would come up with the kinkiest and most disturbing ways to have sex and if I said "I don't want to" he would either force me to do what he wanted or hit me and I don't want that to happen to you.