honestly .. i dont think so. i mean me and my boyfriend have been together for almost 4 years and he says he would never let me do that, but all of my other girlfriends say that their boyfriends like it sometimes. so idk? but i think once in a while is okay i guess, but if that's all he wants you to do then i'd be like WTF? but i don't think you have anything to worry about. it's normal during sex to experience different things after you've been together for a while.