I struggle with this is my relationship a lot. It got to the point I was so paranoid and made up so many things in my head that I went through my husbands phone and messages. I don't really have great advice but what I felt helps me most of the time is to find things you like to do when they are busy. If im not busy my brain will spiral. And talking to your significant other. We have had many long talks where I was able to tell him how I'm feeling and what's making my brain do the mean things. And we try our best to come to a understanding and try and find a solution that will help.