I have a way higher drive than my boyfriend... what to do?

I've been a relationship with my boyfriend for over two years (we're currently in college). We have plenty of opportunities to have because he has a single dorm, but we only have once every week or two. If I could, I'd have every day. I think about having all the time. I masturbate all the time and am like perpetually horny because I'm not satisfied enough with my life. I find myself initiating sex all the time, or if he initiates, it's because I've recently mentioned that I want to have sex. I get turned down, mostly because he's tired or has too much work to do. I just don't understand. I willingly give him often to try to make him want to take it further, I try to do most of the work during sex so he doesn't have to feel tired, I try all sorts of things. I'm so frustrated because I feel like sex is beautiful and connects us in ways other things can't and it's relaxing and pleasurable (obviously). I'm so tired of ALWAYS initiating sex and only having sex once a week. I just don't know what to do. I need advice please. I wanted to ask you guys in Men's Health because you would know best =]