Should I keep going with this or end it completely?

I had a colleague I fell really hard for at some point. He always kept me at a distance, messaging or approaching me only occasionally at work. About a month and a half ago, he said something in a conversation that really got to me—he’s very intellectual. Plus, I was lonely at the time, and he was one of the few decent options left; nothing worked out with others for different reasons. My mind latched onto him, and I suddenly felt the urge to get closer.

It worked for a while. We started going on dates, there was flirting, and I could feel things moving somewhere. Then, after a month, I realized we were still just at the stage of mutual liking, but I was falling for him even harder. I even started bringing up the topic of us directly. He first admitted he didn’t know if he saw me as a girlfriend or just a friend. A little later, he said he’s leaving for abroad in a couple of months and doesn’t plan to build anything serious right now. Then I found out he also thinks I can be a bit of a problem at times, that I’m drawn to emotional highs and lows in relationships, that he doesn’t feel strongly enough about me, but that I have a few good qualities and attractive looks.

Now I realize this isn’t even a story where external circumstances keep people apart—it’s just unrequited love, and I’m way more invested in him than he is in me. But purely on a chemistry level, I’m still drawn to him, and because of my emotional investment in the moment, he’s starting to feel it too. I enjoy the attention in the moment, but when I’m alone, I face the harsh reality and see that there’s no real reciprocity or future in this. Besides him, I don’t see anyone else I could picture a potential with right now. I’ve tried looking for someone else, but so far, there’s no one.

And I’m scared—what if he leaves, and I end up completely alone? I even broke up with my boyfriend because of this fling, even though my feelings for him had faded earlier. I just liked that someone truly loved and waited for me… and now there’s no one. I don’t know if staying in this half-relationship is destroying me even more or if it’s at least some temporary support, even if it comes with anxious thoughts, even though everything seems so obvious.

How does this even work? I want to believe that this "partner" isn’t secretly looking for someone better elsewhere. It would be hurtful… or maybe not. I’ve lost track of my own chaos. The moment I hear a song associated with him, smell his cologne, or see his photo, I calm down. But when I start thinking about the future, I feel awful. I’ve stopped making plans.