my boyfriend is insecure about my past

Me and my boyfriend have been together almost six months now. I have been honest with him since the beginning about my past and the fact that I have had a a lot more experience than he had before meeting me.

At first he wasn’t bothered by it, but over the past month it’s been really getting to him that I experienced all the things I have with him, with someone before, whereas he is experiencing these firsts with me.

He gets really upset thinking about me with other people and I constantly feel like I’m apologising to him for things I did before I even met him. He says he doesn’t want to keep feeling like this forever but it’s just getting more amplified the more he cares about me.

Any advice about how to get past this would be greatly appreciated because I really don’t know how to make it better.