What To Do?

Okay ladies, my SO and I are both 'young' (20) and have been together going on 3 years.. When we're good we are GREAT - but when things get bad they are completely horrible.. I know all relationships have their ups and downs but he practically begged me for our child (10 weeks pregnant today) & it seems like since we found out we have been arguing nonstop about the dumbest things.. Like when he drinks his mouth and attitude get ridiculous and that's something I cannot stand.. So tonight he has been drinking he asked me to stop him by his friend's house (mean while getting out the car screaming fuck you, all this & that) So I left him... But I did go back and told him if he chose not to come with me don't bother coming back to the house because we are done - he chose to stay... Now I'm pissed off & upset like how do you do this to your pregnant girlfriend? I'm so infuriated I just don't know what to do anymore..