Okay, check it out. He broke up with you? A month after he breaks up with you, you sleep with someone else. Were you still talking to him? Trying to get him to come back? or was there no contact during this time? If you were begging him to come back, and then slept with someone else... the person you should be concerned with is not your ex, but yourself. You don't know what you want. Or even worse, you only want what you can't have...