He broke up with his girlfriend for me, but I don't think I want to be with him. What do I do?

Anonymous
I befriended a guy at the gym I initially developed feelings for, but discovered he had a girlfriend. My feelings for him eventually died down. However my friends think that he's interested in me. I flat out denied it. There was a rumor going around that we were together, so I started distancing myself from him a little, out of respect for his girlfriend. After a while though, I couldn't deny that some of his actions indicated interest. He always makes it a point to touch me, and always comes find me when he sees me. I am one of the only people he talks to at the gym.

He hardly ever mentions his girlfriend, and when he does, it's always negative. He told me a month ago that they've been fighting a lot. I asked him why and he wouldn't tell me. Now they are broken up. He was very hesitant to tell me why, but eventually said he ended things because of his strong feelings for me. He didn't tell his girlfriend the real reason.

I guess I didn't give him the reaction he was hoping for. I was shocked, and ultimately felt guilty. I had a hunch that he liked me, but was hoping I was wrong because he had a girlfriend. I feel very guilty because I feel like I broke them up, even though I never asked him to. I even defended his girlfriend to him a few times. I've never met her, nor do I know much about her.

I don't know what to do. I can't say I'm 100% over him, since I always have lingering feelings for everyone I've ever liked. I know I don't want to be his rebound. But I also don't want to hurt him. he's become a good friend, and I don't want to lose that. But I don't think I want a romantic relationship with him either. I feel like our relationship has already changed. What do I do?
He broke up with his girlfriend for me, but I don't think I want to be with him. What do I do?
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