I regret friendzoning him and I think I love him, what should I do?

2 years ago, I met a guy who soon became a friend of mine. After the first year we were good friends and there was nothing more to it until he began hinting that he was attracted to me sexually and suggested we become friends with benefits. I'd always liked older guys and he was a year younger than me I hadn't thought of that but I soon did. After a while I agreed. In accordance to our agreement it was 'no strings attached'

This changed after a few months. I must admit, our sexual relationship was going fairly well we were having fun. I put it to a halt when I started seeing this other guy. I was prepared to date him, that is until my friend expressed his feelings for me. He knew I was seeing someone and it had me confused when he chose to tell me this and asked me out at that point in time. I have to admit, if I wasn't blinded by the other one, I would have said yes but I had to say no. I told him why I had to reject him, he asked for one last kiss and as silly as sounds, I felt a spark in that kiss. I now highly regret it. The one I went for hurt me so bad during our relationship that ever since we broke up, all I have been thinking about was the friend. We haven't been in contact for a few months now and it's been tearing me apart. Not a day passes that i don't think about him and just today he texted me. That text made me feel overwhelmed, like he hasn't forgotten my existence and I'm just so confused. I don't even understand how I feel, how should I go about this?