Many many partners

My boyfriend that I have been with for almost a year now has been with at least 50 girls.. thinking about it destroys me because I know I'm not the best and knowing what he had before kills me, it actually physically hurts 😳😳 he's told me multiple times it shouldn't matter and that I shouldn't even think about it but how do I do that when someone constantly brings up his exes.. most of the people he had sex with he didn't even know and he was on drugs at the time, but I just feel so gross, and not good enough for him.. I love him I'm not worried about that but my sex drive keeps getting lower and lower through out the months.. I just want to be active during sex and not think about how many he's been with.. Any advice? Please no rude comments, I'm just trying to feel more secure in my relationship 😳😳😳