I'm sorry you're going through such a rough time. Ending of relationship can be a grieving process and I went through the same process in my divorce.

Your breakup occurred very recently and I think it is hard to analyze right now what exactly happened during the relationship or to explore possible causes of the breakup. The question is also if that will really help you right now. Your ex made a decision and you can't make him change his mind. His responses do not sound encouraging that he is willing to make the relationship work again.

I do remember posts from you before about this relationship and based on what you described about this relationship (and I know you won't see it that way yet) this breakup might be a good thing for you on the longer term. You don't want to lose yourself in the relationship; another person can't fill a void of happiness. I think it is not realistic and also not fair to lay such a burden on the other one.

My advice is probably predictable but I think you need to try to move on. Try to do things that you like. In my situation it helped me to engage in activities I enjoyed and (although it was not easy) being around other people.

Good luck and believe me, I have been there and it is rough...You can do it and you will come out of it stronger too.