Questions: Guy's Behavior

For the past couple of months I've been having some friendly contact with a guy. Although he sometimes seems to be keeping his distance, he is contrarily the one to keep the conversation going and shows interest in my life. Even after the parking lot has gone empty, we often still remain a little while longer to talk.

Last night, we were hanging out at the gym and while I was talking to him, he suddenly grabbed onto the punching bag hanging beside us, and started dry-humping it. It caught me off guard, and he could clearly see the surprise on my face. We laughed about it then he jokingly mentioned he could see the surprise in my eyes.

Right afterwards, while we were still in our conversation, he started taking off his shirt, then changed into different clothes. Although I have seen more men changing while in conversation, it was very odd to me he'd do this right after he had his little... moment with the punching bag.

When we left, he mentioned he thought of me as an odd person. Then joked about being odd himself. Asked for my age and was surprised to learn I was younger than he'd imagined.

Thing is, what surprised me most by these acts and interactions is that this man is in a relationship and I do not have the sense that he is in any way interested or attracted to me. Would it be an extreme level of comfort or should I be a little more concerned? Lol.