Why does he give me such confusing signals - am I reading into it too much?

I have this coworker at work whom I was getting along with really well and was honestly crushing on. He seemed interested as well until another new female coworker joined. He started flirting with her and I sort of took the hint that he wasn't interested and that I was reading into our relationship too much. So, for the past week I've been trying to keep my distance (because it still hurts to see him flirt with her), but I'm still friendly and joke around with him.

Whenever I interact with other male coworkers, though, he becomes really cold and stoic with me. It's really not like him and it feels almost like he's jealous. In general, it's confusing for me to make out how he's actually feeling. Do you think I'm reading into the jealousy part and that he truly isn't interested and I should therefore back off?

Why does he give me such confusing signals - am I reading into it too much?
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