Sex sex sex !!!!? Wtf !?

So Im 15 I have been with my boyfreind for about an year yes I know in young so don't tell me what I alredy know !! But I really love him and I'm sure he loves me we have talked about marige..... Ok so now to the topic. Sex at first it was fun it still is don't get me wrong but he doesn't want to do anything fun anymore all he wants to do is have sex I'm just wondering is this what most guys think about doing when your alone with your girlfreind and does it really feel that grate that that's all you would wanna do all day ??