If you were dating someone casually, would you want to know if they were dating other people?

I have a really complicated dating situation.

I’m seeing two people right now. One of them I see multiple times per week, and he knows I’m seeing other people. He is also seeing other people. For a variety of reasons, this is a good arrangement, and we discuss these things openly.

The second guy, though, I see only once a week at most (we have a standing weekly arrangement, but he travels often and is not always available). He has never asked me if I’m seeing anyone else, and I have never asked him. We have never talked about what we want out of dating each other or where it might be going.

However, we recently had unprotected sex, and now I feel like I need to know if he sleeping with anyone else. I realized that I am dreading having this conversation because I am kind of hoping that he’s not seeing anyone else, although it seems very likely that he is.

So, after all that, my question is: if you were dating someone casually, would you want to know if that person was dating other people? Or would you just take the necessary precautions and not discuss it?

Also, this guy is on one of his many business trips and I won’t see him for a few weeks. And the last time I saw him I meant to ask and lost my nerve. Is it unreasonable to have this conversation over email? Should I just wait until he comes home, and try to steel my courage and have it in person?