Trust Issues

So, a little backstory before I get to the real reason for this post. I was in a relationship for five years with who I thought was my soulmate until one night last November, I got the text that it was over. I was cheated on and had an engagement destroyed in one night and never quite understood why it happened. Still never got any answers.

Anyways, fast forward and I meet this amazing guy online. Smart, funny, shares a lot of my interests, and is a caring and sensitive man. He’s an amazing communicator who would rather talk through any problems or discomfort calmly with me than get into shouting matches and icing each other out. Shortly after we met, I was pretty sure I was starting to fall for him. We’ve been doing well, handling situations to the best of our abilities. He’s accepted the weirdness that I still live with my ex until August with grace and has made me feel loved, respected, and trusted. And then today, I get a friend request from his... well, I’ll call her his ex-girlfriend, but from what I was told, she never carried that label. She apparently strung him along and refused to put a name on what they were which then lead to her sleeping with someone else behind his back and breaking his heart. He had told me a few months back that she reached out and apologized to him for her behavior and that made him feel better. She has a boyfriend and as far as I know, she isn’t in our area anymore. But to suddenly have her show up in my friend requests was surprising to say the least.

He doesn’t associate with her aside from being cordial because they do share a group of friends (they’re more his friends than hers and have already stated that they think I’m a way better option for him than she was), but because of what happened with my ex, I’m freaked out. My ex was still friends with his ex for the entirety of our relationship and ended up cheating on me with her. So, of course I’m a bit wary that she’s still in his life in some way. He and I talked about it at length today and he told me that he has no interest in doing that to me, but it’s like, I’ve heard it all before and they’ve always done the opposite. I’m trying my hardest to trust that he won’t get bored and suddenly start reconnecting with her like my ex is and I guess I’m just wondering if my concern is valid or if I’m just being excessively paranoid because of the fact that I was hurt so badly last year by my ex. What would you do if your boyfriend’s ex suddenly friended you on Facebook out of nowhere?