<human>: Give me a shortened version of the text

I just got out of a toxic relationship and really want to be single for awhile. But I've entered into a strange situation with an ex-coworker.  A couple of weeks after my breakup he made a move on me after some work drinks situation, and I ended up making out with him. However, I told him that I wasn't looking for a relationship and that I wouldn't be ready to do that for some time. He understood, and said I should date other people. So I felt okay about continuing to hang out with him and make out with him. I even told him when I went on a date with someone else.

But since then we've had sex and I feel like that's changed the intensity of the situation. Because we've known each other for several years, this isn't just some 3 weeks long level of intimacy. And we hang out several times a week. 

So now I have a date coming up with another person, and I feel slightly weird about it. I don't like to sleep with multiple people at once, so that's out of the question. But I really don't want to end up in another relationship so quickly! What is the etiquette for dating multiples? I've never done this before and it feels like a weird gray area. Is it cool to make out with other people? He said he's cool with it (before we slept together) but he might really be hurt by it. I just don't want to have a talk about expectations so soon... especially since mine are that I want to continue building intimacy without building a commitment yet, but that doesn't mean I'd rule it out in the future.

Also, what's the etiquette for the people I go on dates with? At what date do you mention that you have a regular FWB? Is that even relevant? It just feels kind of shady to not mention it, but it feels like TMI to tell everyone all these things. HELP.
<bot>: Never done casual relationships before. How to handle the weird gray area zone between FWB and relationship potential, without freaking the other person out who isn't just a FWB but an actual friend?