Shame can strike at this point. You don't want everyone to know your relationship has gone down the pan, and you're afraid of what people will say and think. There's no reason why a break-up should make you feel like a loser, but you get the impression you're going round with a big L tattooed on your forehead.
It's a downward spiral which can lead you to question your self-worth. You think you're ugly, fat, stupid, and not good enough for him, which is why de dumped you. This kind of self-flagellation will get you nowhere, so snap out of it: your qualities attracted him to you in the first place so stop telling yourself you're worthless! In time you'll understand why it all went wrong and accept it.