HELP dealing with my boyfriends sex history

I would really appreciate any help or wise words... I have been with my current boyfriend for almost 6 months and I love him very much and can honestly say that I see a future with him, one that I am so looking forward to. But I keep having these horrible thoughts in my mind regarding the fact he has slept with more people than I have. I don't know how many exactly and I don't think I'd want to. I've only ever had the one serious relationship before him which was 4 years and he was my first. Sometimes he may accidently say small comments which leave me thinking of him having been with other people. It makes me feel so uncomfortable and dirty. We have spoke about it and he is very adamant that I am the one he truly loves and no one else compares but I'm still just finding it hard to deal with. I know I may be being naive here and I do constantly remind myself that it's his past and that I am with am now but these horrible sticky feelings just happen sometimes. Silly Thoughts like being out in town and thinking "oh god has he slept with her" and i don't know maybe feeling like a number😅.