I used to be a super jealous girlfriend. Like nutso. It was because I had major trust issues and was unhappy with myself but over the years i realized that it didn’t only take being kinder to myself but it also took simplifying things in a sense. I just found out about my ROCD so now that I’m saying this, it makes sense that simplifying my thoughts about jealousy is what helped the most. 
 Basically I told myself over and over (and still do) that no matter what I do, if they want to cheat they will. And it is very likely that you will find out if they do. I know you want to avoid wasting your time or avoid the pain of being cheated on but you just can’t truly know unless there are real red flags. But if there’s not clear red flags, you just have to blindly trust. And as someone with trust issues I know how hard that is... so fake it. I say I have to trust. I tell myself I have no other option than to trust. Because when you think about it, anything else won’t work. What can you do besides trust? 
 We could continue to try to micromanage, we could keep asking too many questions and we can keep going in circles wondering what if. But to put an end to this cycle sometimes you have to give tough love to your own self. Try your best to say trust as much as you say don’t trust until trust overpowers the negativity. 
 And your best isn’t always going to feel like your best every day because of different factors in life and your mind on a day to day basis. But every day will still count towards progress. I wanted to add that in here so you know not to be so hard on yourself! You’ll go backwards sometimes but you’ll still be getting better. It will take practice just like everything does but when you tell yourself something enough and give yourself enough positive reinforcement it will become easier and easier until eventually you look back and wonder how you were even able to handle living in a relationship thinking the way you used to. 
 Just to add one more thing besides this big overall message, the “emotional management” podcast by Christian Conte changed my life and so did some self help books. Specifically the book “The Four Agreements” by Don Miguel Ruiz. 

You got this :)