"I Just Don't"

I met this amazing guy that I work with and we became good friends. He would always come over to my work area to talk to me while I worked and he followed me around my department while I ran around working, so we could continue to talk longer. We really got along well and had so much fun together. We text back and forth all the time, in and outside of work. Based on his actions and behavior, I was almost positive that he had feelings for me. Researching A New Mode’s articles on how to tell if he likes you, he met most of the criteria for liking me. I was excited and curious because I had developed feelings for him. I finally worked up the nerve to tell him how I feel about him and asked him if he felt the same way about me. He said he was sorry, but he didn’t feel the same. I respected his honesty and we remained friends. Everything went back to normal, except I continued to have a secret crush on him. Oh unrequitted love! Ugh! Several weeks later, I worked up the nerve to casually ask him for feedback and just wondered why he didn’t feel the same. His response was confusing to say the least. “I just don’t.” Thinking maybe he didn’t understand the question, I listed out a few reasons why I thought he didn’t feel the same way and he said it wasn’t any of those things. He said he didn’t have an answer to my question, he just didn’t feel the same. I respected his answer and dropped the subject, but I’m having a hard time moving past it. If he doesn’t feel the same, that’s fine, but if you know why you like someone, wouldn’t you know why you don’t like someone? I’m trying to come to terms with it for closure, so I can move on, but I just don’t understand his response. Am I missing something? Any thoughts on the matter would be greatly appreciated.