Sex drive is super low

I don't know why but I don't like sex that much anymore. My boyfriend and I have been arguing a lot about it recently because he wants to have sex at least once a week.. But I'm just not horny, and don't want sex that often. Sex for me has started to feel like a chore. We used to do it a lot, but for some reason I don't like it anymore. Is something wrong with me? Maybe hormones? How often do you guys have sex with your partner? And how many times should we have sex to keep it a healthy relationship ?