Jennifer's comments are great and i agree, and heck who hasn't been there, but. yes i have a but, i am great at playing devils advocate so here i go.
relationships are about give and take and after all you did get involved with this man and i would hope it wasn't just so you could try to change him. Did this behavior bother you before or is it somethign that has just been comeing up since the baby, and pregnancy?
how much of what he does would be a problem if you trusted him? and why don't you trust him, is it something specific or more jsut how you feel, don't let your own insecurities make you distrust him, it isn't fair to either of you.
and what kind of parent is he?
put yourself on the other side, he lies to you because he doens't want you to get mad, and you get mad because he lies to you and you don't trust him because he lies but he only lies to you because you don't trust him. his friends are girls ok, that doesn't mean he loves you less and they were his friends when you got together as well right? you can't really want him to give up his friends for you that isn't fair regardless of thier sex. but you have this pattern between the two of you of negative and detrimental behavior and you both feel justified by how you are feeling, if you break the pattern then the relationship can be saved, you try to trust him and not get mad when he goes out and he will then tell you what he is doing so the lying stops and you feel like you can trust him and things are better, you create a pattern of trust and communication instead of one where you are both struggling. good luck in whatever you decide but so often we throw in teh towel over something that can be fixed if BOTH people are really willing to make the changes and take the time and give a little.