"I'll see your heart ...
I've had this exact situation happen to me, so I can speak from experience.
The wounds have healed and the scars have faded. He should be gone from your head, but unfortunately he was a big part of your life, so he's not going to be that easy to get rid of. You are genuinely happy for him and his girlfriend but the 'what-if?' scenarios play in your mind like a horrible, unescapable play.
So, my advice is to forget the dreams, don't encourage these thoughts. You had your chance with him and it was his loss that he didn't take it. Now all you have to do is give yourself the room to get rid of these thoughts. Try concentrating on something or someone else?
… and I’ll raise you mine"