AITA 50th CLASS REUNION

Wondering if I am justified with my feelings. My husband of 45 years 50th high school reunion is coming up, we last went to his 10 year reunion. We had planned to go to his 25th, but his old high school girlfriend reconnected with him prior too, and he left me and moved in with her and went to the 25th reunion. We ended up getting back together. My husband told me he was going to the 50th reunion and if I wanted to come, at first I said yes if his best friends wife was going, and she was, but the more I kept thinking about it, I am not comfortable attending the ex will be there and so will everyone from the 25th. So I told my husband I wasn’t going as I feel uncomfortable he said ok, well yesterday I saw he charged his ticket and a second ticket for someone in need. I asked him if he understood why I was not attending and he said cause I wouldn’t know anyone and I said that is not the reason I would know people and have no problem attending events where I don’t know people. I explained to him it’s that his ex will be there etc. His only comment “well I regret that”.
I am now upset and sad, that he doesn’t understand how this hurts me. Am I justified in my feelings, should I suck it up and go, should I just stay home and have him go without me or ?