Need help with something.

So ive been dating my boyfriend for almost a year. We’ve signed a lease and move next month. Our relationship is fantastic. We don’t fight we get along really great. We communicate really well and have discussed things that are important to us in our future. Even discussed marriage. Last weekend we were discussing this concert we’re supposed to go to with a bunch of his friends. He wanted to make sure I was okay with going because his ex will be there. They’ve remained civil with each other and are friendly. Then he goes to say well you’ve already met her. At my friends wedding. Later that evening I said to him in the future I’d like to know who I’m meeting and he should of told me ahead of time. He said he honestly wasn’t thinking. She was in the wedding from the start they weren’t partners and he barely saw her. He forgot to tell me that day because things were so crazy. I know he loves me, and I know he wouldn’t cheat on me. It’s me who needs help, I’ve never dated someone who was friendly with their ex. It’s not like they text or hang out. I just can’t help but feel self conscious about myself, I don’t remember what she looks like but I always feel like less than other females. Also they dated when he was 25 and he will be 30 in August. Just need some advice.