Why does my boyfriend always want to have sex?

We have been together for over 2 years. At first I just thought it’s because we just started dating, and that he would eventually stop wanting to have sex all the time, but he still wants to have sex everyday almost and sometimes more than once a day. I like having sex, but not everyday and when I tell him I don’t want to he gets upset and sad. I know this sounds ridiculous, but can someone please tell me what I should to get him to understand I do like having sex but not as much as he does.