There was a time in my life that I was a very jealous person, constantly thinking that my partner was cheating. I had that paranoia so bad that I would be going through the trash, the pockets, the cars looking to find that one shred of evidence to support my belief- which I never did find one. It was all I can think about which drove my anxiety to crazy levels.
It was a relationship killer. This went on for years.
I've learned to control it by realizing that I'm more than what I give myself credit for. I had a very low opinion of myself- self esteem issues, I felt disposable. "Why would anybody want me? I don't even like myself". It was hard at first, but I kept believing in myself that I'm worth more than that and that my partner wasn't the evil monster my head was playing them out to be. My head was using them as a weapon against me, another way to beat myself up.
Every now and then, I can feel that paranoia starting to resurface and I would shake it off telling myself I'm being silly and make it go away. It was a constant battle at first before meds, but now stabilizers helped put it away.
I hope you get the help you need and sleigh this dragon before it ruins your life.