Guy's Behavior

Does it make sense that a guy would be territorial over a woman who he's only had sex with once? Especially when he is in a relationship with a woman?

Backstory: This guy cheated with me a couple of years ago while he was in a relationship we only had sex once. But a year later he wanted to have sex again. But I didn't do it because I thought he was trying to cheat again.

Anyway I usually see him where he works because he works at a store that I go to. A couple of months ago when he saw me talking to another guy (his coworker) he came over to where we were and interrupted our conversation. He overheard this guy name Rick (his coworker) telling me that he had done something fun. And then he came over and stood between us saying (how was it?). Then he picked up an item that was hanging on the shelf. I don't know why he would do this especially when he told me he didn't think it was a good idea for me to practice massaging him. He said he would love for me to practice on him but that was trying to be a good boy. So why would he act like this when he saw me talking to another guy?

Does it make sense that a guy would be territorial over a woman who he's only had sex with once? Especially when he is in a relationship with a woman?
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