Am I overreacting? UPDATED

My boyfriend and I have been together for 2 years and we have plans to get married, buy a house and have kids. We live together now. We both had really bad breakups before we met. I got cheated on by my ex and I accidentally caught him at a bar with his ex girlfriend. My boyfriends ex was always dumping him and going back to him when she was bored or needed something. Anyway that ex sent my boyfriend a message and they made plans to hang out as friends this week. My boyfriend told me about it and I got upset. My biggest fear is getting cheated on with the ex and he knows how hard it was for me when that happens as him and I were friends at that time. I have a bad feeling not about my boyfriend but her I read the messages and I feel like she was being flirty. She wants to meet up “where we first met.” I really am upset. I don’t want to be controlling but I just can feel that she is trying to get him back. I told him how I felt and he said the whole “you’re my world, my one and only I wouldn’t cheat on you. We have plans and goals that were working on. I love you so much. It’s just as friends.” I feel so disrespected I’m hurt, and I feel like I’m not enough. I trust him but a major part of me is no able to shake that she’ll get him to leave me. Let me also add that I gained some weight and I feel very insecure anyway at the moment. I obviously would rather now before we get married but I don’t know what to do now. He’s my best friend. Also ironically this time of year was when I caught my ex with his ex because I was out with my family for my tias birthday. Update: I’m also going to add that I don’t care if he’s friends with other woman. He has other female friends. This situation in general makes me uncomfortable.

Last update: He told her he wasn’t going to hang out with her.