My ex won't even talk to me. How can I get him to respond to me? I'm so hurt I don't know what to do.

I think some more information is needed here for anyone to really advise you.

1) why did you break up?
2) who ended it?

Ultimately you can not make someone talk to you if they don't want to. You may come across as desperate or only serve to irritate and annoy them further.

He is most likely a jerk, its happened to me... get a hot guy to be all over you in front of him and he'll talk to you...

He is an ex for a reason. He is not obligated to talk to you or communicate with you. You may be hurt, but why are you hurt? There is no reason for him to communicate with you when you both are separated.

Maybe he is to hurt by the break up, and needs time. He is an ex, leave him alone.