I'm in love with somebody that isn't able to fully love me back

I met this guy when I was 15 he was 18 and we were in high school. I like him from the moment I first met him. He and I ended up dating about a year later. We dated for about 4 years off and on in a long distance relationship. I loved him with all my heart. Nobody could compare with him just the distance was hard. After a while I decided that I needed to move on. Even though I moved on he was always in my thoughts, my dreams. I have never felt this connections with anybody else. So I had to stop being his friend even trying to get him out of my head so I could move on and be happy with somebody else. Well that didn't help I still thought about him all the time. I got married eventually and decided to look him up again. He had gotten married to and we became good friends again. My marriage stated falling apart and I was always thinking of my first love. How things might have been if I would of just stayed with him. I envied his wife and missed how much he used to love me. We kept getting closer and closer. His wife doesn't understand him and I know him better than anybody. He tells me he never stoped loving me but he wants to try everything to save his marriage. We have never has sex during this time. I am trying to be a good supportive friend likes he wants and stop obessing about a man I can't have. He really does care about me and I respect his wishes and would never want to break up his marriage but on the other hand I want him for myself. This has been going on for like 2 to 3 years can somebody help me?