boys, babes and break

I have been dating my boyfriend for over a year and we are very close (we both have family not accepting of mental illness so when we both had depression we relied a lot on each other). I love this boy to death  and I can see us being together for a very long time. 

A bit of backstory, in our friend group he has dated three of the girls (throughout middle and high school) and one of the other girls in the group he told me (before we were dating) that she is the only person he has ever loved. Now he feels that he truly has a better sense of what love is and he knows that wasn't it, but he's had strong feelings for this one girl specifically. At the beginning of our relationship it was really hard because she didn't like me and thought I was too broken to be fixed, so her and I have had some bad blood in the past (were all pretty good friends now). Also I met my boyfriend on spring break and at the time he had a girlfriend and while he didn't flirt with me or cheat on his girlfriend in anyway, him meeting me on break was why they broke up. 

My question now is he is going on break with all of his guy and gal friends (including all the gals mentioned above) and i am going wth my family. I am a worrier and I've already been freaking out and having nightmares because I don't want to lose him. I trust him and he tells me all the time that he will try his hardest to never do anything to make me want to break up with him and I love him, but what would you guys do in the situation? Would you set ground rules or talk to the gals or what? I just don't want him to meet someone new. he's certain he wants to marry me, but that could all change in the blink of an eye. And if he cheated (although I never would think he would it's just not his character) I know I would have to forgive him because he's all I've ever wanted out of a guy. 

I NEED ADVICE!!