How do you control your emotions when it comes to your mans past relationships/sexual partners? I'm pissing myself off😒

I'm very secure in my relationship with my boyfriend. We have a very very good relationship. Tonight things got brought up somehow and the fact that he was his ex's first and she was his got put out there... I cant explain why I feel the way I do but I honestly feel so mad and sad and insecure right now. He was with her for three years and they were each other's first😔 I understand that it's wrong to be mad or upset ab his past because I literally have a past too🤦🏽‍♀️ but I absolutely hate the thought of him being that close to her and giving his virginity to her and hers to him. I wish he wouldve been my first and I wish I wouldve been his😔