His Name Triggers Me

My ex and I broke up 2.5 years ago and we ended up staying really close. We weren't seeing other people and the breakup happened because our parents didn't approve our marriage. For a little over 2 years we were each other's closest confidants and spoke all the time.

A few months ago he started looking into a particular marriage proposal and he told me he would let me know if it got serious. He promised he wouldn't vanish off the face of the earth and I trusted him. We kept speaking all the time.

Fast forward to the week that changed everything -

He forgets to tell me his engagement date is fixed. I find out because he says his parents are going to the girl's place to finalize the details and I ask if it's fixed? He goes yeah I thought I told you. A week later he asks for no contact at all for a week since he's going to go spend some time her and needs to be in the right headspace. No space for me to react whatsoever.

We're back on talking terms now but everything feels so messed up. He comes off as guarded and formal and it really hurts. I just end up feeling like some random ex troubling him. I used feel excited and butterflies each time I saw his name flash on my phone. Now I get anxious and I really hate it. I have nightmares where he continues being this fake formal version and it just hurts. I feel he's broken my trust and I'm not sure how to heal. I really want to be okay because this person is super important to me and don't want to lose him. But it's really taking a toll on me now.

Any suggestions?