Please help..

My husband wants to have sex a lot. Everyday. All day. We are 20, and it should be normal to have sex all the time right? I am never in the mood.. I never want to. I'm attracted to him very much. We've been together since 14 & we've had sex since we was 16. What do I do? We've tried doing different things to spice it up and do things to make it fun. But I'm never in the mood? I never want too. Why? What do I do. :(?