No sexual appetite?

I know it's normal to go through cycles of wanting to have sex and not, but this has been going on for almost the whole summer! And I'm 20, I feel like I should have a healthy sexual appetite. This really upsets me and obviously my boyfriend. I just feel horrible because I feel like I can't please him (I know that's not the point of sex, but it doesn't hurt to make him feel good too obviously) and its putting some strain on our relationship. I miss how we used to be able to have sex on a drop of a hat notice and above all else I miss the intimacy. Does this happen to anyone else? Any tips?