I am so heart broken... what should I do?

On last Monday my boyfriend of 4 years broke up with me. We have a daughter who just turned 3 on Thursday and our anniversary was on the Sunday before he broke it off. On that last Saturday he was out with his friends for all night and his lips smelled like u know what... so, anyways, yesturday I dropped my daughter off at his grandmas house and he wasn't there to watch her while I was at work and she was actin crazy so I went to the bar I know he goes to (mind you this is 7:50 in the am) He was there and I was goin to ask him to get her but I walked in and saw him kissing this blonde icky girl! My heart broke, but not before I punch him several times... my question is... what should I do now? I have a beautiful daughter, but that turns guys away... I'm only 23... I feel like no one is ever going to love me. How could he dump 4 years of our lives and treat me like a dog~ I feel like I have been traded in for a better model.