I don’t know what to think

I’ve been with my boyfriend since 2014. In 2016 he cheated on me and we took a break for about nine months or so. Then we got back together. It’s been two and a half years and sometimes I still get upset when I’m reminded that he did have sex with someone else. The thought drives me crazy and literally makes me want to vomit. But. When I dont think about it, I enjoy him, I love his laugh, his voice, his smell, the way he treats me.. what does this mean? How do I get over this? Every time I mention it with him it gets weird.