I can’t be comfortable during sex

When my boyfriend and I have sex I just want to get it over with really fast and that’s it I’m not how I use to be I don’t feel like doing the most or being a complete freak or anything like that with him like I use to I feel so uncomfortable. We have been together going on 4 years but we broke up for 8 months in between that time and since we got back togeather the sexhas been the same on his end yes but not mine I feel disgusted like I don’t want to have sex because I know and have heard stories of who he fucked and where they fucked and all that when we were broken up and now I feel like I can’t give him all of me. Then sometimes when I do go all in and I happen to moan later during the day he will mess around and try to be funny and imitate me moaning from when him and I had sex and I just feel so uncomfortable and say see that’s why I don’t like to have sex with you. He always wants to have sex but I have yet to tell him why I always push him away and decline him. What should I do and what do you think? I know it’s about to be New Years and my mindset should change but my feelings haven’t I’m still so disgusted. Any advice? Any one can relate? I do love him but damn.