Ah, so he has a girlfriend.
This explains the fact that he won't say how he feels. At the moment he is getting his cake and eating it - he has the security of a relationship, also he has the excitement of a flirtation.
I was in a really similar position to you about 10 years ago. I fell in love with a guy while I was with someone. I split up with my then boyfriend and the guy I had fallen in love with was then in a relationship with someone else. The whole time we were in touch we had a bit of an "emotional affair" going on - but never discussed how we felt - it was just all about subtext and frisson, long phonecalls and letters, long walks along the South Bank etc...
In the end I had enough and brought it to a head. I told him how I felt and said things couldn't continue how they were. It was painful and very sad, but it just brought about the inevitable - that he would chose his girlfriend. This would always have been the case. I was just his "grass is greener" that he could have self-indulgent fantasies about - it would never have gone anywhere.
Once I had established nothing would ever happen, I broke all contact. It was totally the right thing to do.
I bumped into him a couple of years ago. They got married, had a beautiful son. I met someone and got married myself. I have a beautiful daughter.
The "love of my life" who I went through all the heartache with has not aged well at all. He is so obese that I did not recognise him at first. Speaking to him again, I realise that he still skirts around issues. We bump into each other from time to time and what happened years ago is like the elephant in the living room because it will never be discussed because he doesn't like looking at feelings head-on, so it will always be a source of embarressment between of so we will never be friends (probably just as well all things considering).
Anyway - seeing him years later with the benefit of hindsight and more life behind me, I see that bringing matters to a head and just getting on with my life was the best thing to do, that the things that seemed mysterious and romantic all those years ago would have just been a pain in the arse in the real world.
Honestly, I know it's painful, I've been there, but it's really not worth wasting any more time on this guy. Better things are out there on the horizon for you - go grab them!!