Jealousy and relationships

My boyfriend and I took a break for about a year but I’ve known him for 3 years. Long story short we were together and then he had to move for work. Long distance took a toll and the break/breakup happened but we realized we wanted to be together through it all a year later. We had the talk which we shouldn’t have had about if we were with other people when we weren’t together. I know of at least one person for him. And even though I was with other people too, I’m extremely jealous about it. Like it’s always in the back of my head I get so jealous I lose sleep over some things. It’s not healthy and I know it. I’ve always been a jealous person. I can’t help it. But I need tips on how to just get out of my head about it because we are together now and are planning our lives together through the long distance.