Cheating in a Distant Relationship

My boyfriend (23m) and I (22m) have been in a long distance relationship since February after meeting on a dating website a few months prior. Very recently, I let a guy I barely knew go down on me, and I felt so upset afterward that I called my boyfriend and explained everything. He immediately forgave me, and a couple hours later he called and said he had gone down on a guy a couple months ago. We both agreed that this wouldn't have happened if we weren't so far away but it would never happen again. I'm moving close to him at the beginning of next month, so it wouldn't be hard for me to just not talk to anyone else in the meantime.This past weekend, my boyfriend went out with a bunch of friends and he ended up getting drunk and making out with a guy he met on Instagram. He called me afterward and we talked about it again today, but for some reason this one isn't sitting well with me. He asked if he should tell me when he makes out with guys but then assured me that when I get there, it probably wouldn't happen anymore.I'm suspecting that he wants to open our relationship to seeing other people and learning more about what we like and dislike, but I don't want an open relationship because I'm kind of a health freak. I care about who I share sex with, which means I also care about who my partner has been with in the past. I don't like taking risks when it comes to my body, but I'm afraid my boyfriend has too big of an urge to explore with other guys.Any advice on how to handle this situation? I feel like I can talk to my boyfriend about this once I've established how I feel about him kissing other guys, but for now I just want to establish my own stance on open relationships. Has anyone else run into this in their relationship? For those of you in an open relationship, what rules do you follow, if any?