Wish I would just think the right way

So I met this girl about 6 years ago and we started dating at a very young age our relationship lasted for a year and a half and this was both of our first real relationship. We ran into alot of problems and we broke up for 3 years but stayed in touch pretty much the whole time and hooked up a lot and told each other we liked each other still. In our time apart we both worked on what caused a lot of problems with our first relationship (for me a big issue was trust and being jealous) and then I re asked her out a few months ago and everything's been going great and we have this seemingly perfect relationship which I am very thankful for. We talk abou our future a lot and getting married even tho we just turned 20 in seperate colleges and I think we both could really see it happening like that the only problem is I constantly feel like I want to hook up with other girls and things like that but I don't want to be a cheater. I know it sounds stupid but I'm scared if I do stay with her and we keep this great relationship up for the rest of college and move in together I will always hold it against her that I didn't get to go out and meet new people and try new things experiment and such and basically miss those young party years. I don't know how to sort my head out I just want to love her as much as she loves me and not have those times where I think I want to go mingle and such with other girls. She is the only one I would currently want to move in with and such in the future and I don't want to lose that but I can't help the way I feel even tho I have tried to change it.