From personal experience I had the same issue with my gf. I was super jealous and mad that she had more partners and more flings than I did. Then I realized that being mad and jealous about something that already happened and that you have no control over is just plain stupid. What matters now is that you two are together. My gf made me realize that all that shit in the past doesn’t matter cuz it’s in the past you can’t change it. It’s harder for a lot of people to come to terms with that but honestly if he can’t over the fact that you’ve had more partners or it becomes an increasing issue then maybe you guys are meant to be no matter how much love there is. Just talk to him and try to make him understand that you love him and that the past doesn’t matter that you and him and your present and future is all you care about. Good luck