Guilty

So for the past few years Ive been dealing with guilt. I have been dating the same guy for 5 years, no other boyfriends, and I feel extremely horrible and guilty when i think about anything sexual. Don’t get me wrong I love sex with him but sometimes it’s so bad that we have to stop. It’s really hurting me and I need some advice to get over it. I feel like such a slut but I’ve literally only had sex with one guy. Help?