Losing interest in sex?

Me and my bf have been together going on 3 years now. In the beginning I was crazy for him & wanted to have sex every second. Now I could care less for it and when we do have sex I find myself waiting for it to be over . Keep in mind im in nursing school & also working full time. Instead of sex I rather come home and cuddle up to a movie :( we are in our twenties & Our relationship is great so I’m confused as to why I haven’t been as sexually attracted lately 😕 help

I need ways to bring back that spark