What do you do when the man you love is with another woman and is waiting for her to break up with him?

So, one of my best friends has been in a relationship with a girl for like 8 years or something like that. I have had really strong feelings for him for a long time. He has a girlfriend who he can't stand, and he is very open about this, but keeps waiting for her to break up with him (probably won't happen because she doesn't help pay for anything around the house, so sweet deal).
I sent him "Singles You Up" by Jordan Davis, to which he didn't reply to last night. It broke my heart and I cut for the first time in at least a month.
I just sent him a text telling him I was sorry, and he asked why, but before I got the chance to answer, he called to check on me.
I am more open with this man than I am with even my best friend. He knows music is my way of communicating sometimes.
Last week, or week before, I sent him a text in the middle of an anxiety attack asking him to tell me that everything would be okay. He was asleep at the time, but first thing he did when he woke up was text me back. He was home with his gf and still texted me (they don't sleep together). He knows about my BPD and depression, and does anything he can to help with my emotions. He's 16 years older than me, but I don't care.
Sorry this post is so long. Just had a lot to say about him.