Sort of long-distance relationship problems

Hi everyone, I (21M) and my boyfriend (24M) have been in a steady relationship for a year and a half. We usually see each other once a week for two days (if all goes well) and our sex life is mostly fine. The thing is, given how little time we spend together, it’s not a huge issue for me if we don’t have sex constantly when we are together. However, I personally feel the need to have sex more often, if only to explore my limits and figure out what I actually like. He’s very vanilla, so we tend to do the same things over and over again.
Next week is the last time I’ll see him for a month. Regardless of everything, I’m just very curious sexually, and since I’ve had very few experiences, I really want to explore this world that’s almost completely unknown to me. I’m not sure whether suggesting we open up our relationship (just sexually) is the best move for us. From my point of view, it would be ideal: that way, when we’re apart and I feel the need, I could just comfortably meet up with someone, sleep with them and that's it, without any strings attached. His perspective, however, really worries me. I intend to talk to him about this next week and hope for the best, but I'd love to hear some thoughts