Concerned about how my ex-boyfriend is taking our break up?

So long story short--things just weren't working out. And they weren't working out for a long time. We dated almost 4 and a half months but the last month or so of that was just a very unhappy and unhealthy relationship. His immaturity and insensitivity and stubbornness was just getting to me. I had started thinking about wanting to break up with him just a little at first, brushing the thought away, wondering why i would even think such a thing. But i just kept thinking about it more and more until i was just thinking in my head--OHMYGOSHWHYDONTIJUSTBREAKUPWITHHIM… So I finally decided, two days ago, that we should break up. That week we barely talked...we never held hands or hugged. We both kept our distances. But that week especially, was the week when he seemed to try to be uttermost annyoing he possibly could. So I broke up with him, yesterday. The break up actually went quite well, resulting in smiles, a hug, and of course the standard "Let's just be friends". But keep in mind, this was my first relationship, and i had noo idea it would end up this bad. He is taking the split very, very hard. Won't text me back, completely ignores me. And I'm taking it pretty bad too. I spent most of yesterday afternoon crying. So to get to the actual question, what do i do? Guys, what would you want your ex girlfriend to do? How long do I give him space for? When will we be able to talk again? Why are we both taking this break up so hard..when it seemed like the right thing to do? Please any advice is appreciated, thanks.