I've recently been a situation similar to yours. I'm sorry for the pain you are feeling and must have felt for as long as this has been going on (for me it was 1 1/2 years (cringe I know)

It took a lot of feelings, some tears, and a friend introducing me to the idea of radical acceptance that helped me quite a bit. I think what it at least made me do was assess the pros and cons of the relationship; for me the cons far outnumbered the pros and i think that helped me accept that I was so excited about - and fighting for- something that exhausted me and was certainly not going to get what I wanted.

The next step for me was just dialing back communication a lot - that has made it easier for me to both keep in touch with someone I care about without getting excited about something I've accepted is just not going to happen right now. Hope this helps. *hug*