My bf (18M) keeps talking about my past (18F)

My boyfriend had one girlfriend before me and he says it wasn’t really searious. I had 3 exes before him (2 of them being kind of long term) I am his first love (that’s what he says) and he lost his virginity to me but i haven’t lost mine to him.
All my exes treated me really badly and i told him that so he says that its annoying that they treated me badly and i still stayed and gave them what they want, but he treats me amazing and if he ever did anything, i would stay. He said he “doesn’t mind treating me good but everything hes doing, if he didn’t do, id still be with him” which i really don’t understand.
He also said its annoying that im his first and hes not mine which i do understand but i can’t change the past now. Hes been mentioning my past for months now and i really don’t know what to say and i feel like this will be the reason for our break up in the future and i really don’t want that to happen i love him so much, so what am i meant to do/say to ease his mind or make him just stop thinking about my past?
Another note: he says he has retroactive jealousy
He also says he tries not to think about it but he always thinks about it.
He gets mad at me because apparently i used to be too “easy” in the past and my ex didn’t do anything to deserve sex but my bf now did and i still didnt give it to him until after 5 months, but then he says he didn’t care about sex which doesn’t make sense because why are u complaining then..