Boyfriend seems uninterested sometimes.

So I'm 17 and my boyfriend is 21. We have had sex before and it's AMAZING. We have a awesome relationship and he's so sweet. Everything is great except he never really makes a move. He never initiates anything with me, I have to initiate it with him. And sometimes when j start kissing him or something he tells me to stop. He says it's because my mom is home but we've done stuff when she was here before. I just wish he would start stuff with me. Opinions?