<human>: Could you distill the essence of the text into 1-3 sentences?

We've been together for a year and a half, and been good friends for going on six years. I love him to death, he makes me happy, all that good stuff. 

Here's my problem. 

My past two relationships were very unhealthy and at times abusive. I was constantly cheated on, lied to, manipulated etc. It was a rough time, but I got out of it, took several months to get myself back together, and that's when I decided to start dating again. And then life happened and my SO and I ended up together. 

In the very early stages of our relationship, he had a brief affair with his ex, whom he had been with since our sophomore year. I was heartbroken, he was angry at himself, and it was just a mess. We tried to patch things up, but there were still some road bumps. Eventually we both sat down and talked it out, took a week away from each other without any contact (as opposed to seeing each other almost daily), and in the end got our shit straight. He went completely no contact with his ex, blocked and deleted her on all social media, and put all his effort into repairing our relationship. 

It's been several months now, and we're better than ever. We're moving towards getting our own place, starting careers. All that good stuff. Trust has been rebuilt on a logical level, and I feel great about the future. 

My issue is, thanks to my severe anxiety issues and shitty past experiences, I get random bursts of worry that he'll leave me/cheat on me/something of that nature. I know it's probably all chemical, because logically I know he isn't. He doesn't hide anything from me, we can talk about anything. I'm currently not in treatment for m anxiety due to insurance issues, and I know that will help. But what can I do in the meantime? Is there anything I can do to talk my thought process out? Maybe something he and I both could do to help me chill out? It really is a random occurrence. Nothing sketchy triggers it. I'll just be sitting there, and out of the blue, my brain goes into panic mode.
<bot>: I know my almost fiance isn't cheating, but my anxiety likes to randomly try to convince me of such. Help.