He's heartbroken too so why doesn't he ask me back out?

He's probably trying to sort out his feelings. Was it his first relationship? There's no surefire way to "get him back" but begging for him back won't help, it'll just drive him away. So, you have to be counter-intuitive. First off, write a short hand written note saying that you agree with the break up (for now) you still care about him and tell him something positive happened in your life and you'll have to tell him about it later. Also let him know that you're there whenever he needs to talk. Then wait! Don't call, text, nothing for about a month. Wait for him to call you but in the meantime go out with friends and have fun. All this does is it erases the bad feelings associated with the breakup and he'll forget why you broke up in the first place.