I don't understand it. I've never hurt like this before. What am I going to do?

I think there are two possible outcomes her. First, he will get over himself and realize he made a mistake and want to get back together with you. If that happens you will have to consider weather you want him back. Second, He can't seem to cut the umbilical cord. There are many men out there like that and if that is the case you will be better off without him because that will be a constant strain on your relationship.