No sex drive

Okay so I'm 19 and my boyfriend ,also 19, and I have been together for 2 years. He was my first partner and when we first had sex , about a month into our relationship, we literally did it ALL the time and I loved it. However for the last couple of months my sex drive has been decreasing and I never want to have sex anymore. I literally never want it anymore. It's not that I'm not attracted to him because I very much am or that I don't want to be with him because I love him so much and can't picture myself with anyone else but him so I have no idea what my problem is .. I used to enjoy sex so much and now it just feels like a chore and I'm not into it I only do it because I know he wants to. Idk if it has something to do with me being a little more stressed since I left for school or what but I need answers and help . Has this happened to anyone else ? And if so what do I do how can I overcome this ? I want to enjoy sex again and bring back my sex drive so please share your advice . Thanks ladies !