Snape, he has done the lazy man thing - you and he have had all the relationship thing under the guise of friendship. He hasn't had to work at a proper relationship, you have given him all the things we say we miss, companionship, hugging, talking everything bar the sex
Does he have longterm relationship history? He sounds to me, (and I am possibly totally wrong) to be emotionally stunted
I would advise you to really think long and hard about how you go forward now. Is he likely to remain single forever? Could you have a friendship where you could cope with his dating and coming back to tell you his relationship woes?
He obviously loves you as a friend but if he was in love, you wouldn't be feeling wretched today, you'd be together. It's so painful but I think you need to step away, maybe not forever but definitely for now.
You have us and this thread to get you through