Keeping it together?

How do you ladies keep it together with all the stresses we are now exposed to? My son is very difficult and has been since he was born. He isn't a good sleeper, just screams for no reasons, horrible napper... all my SO and I do now is fight. I have my son all by myself a majority of the time. I don't have a lot of patience and just find myself extremely stressed out and unhappy. I really don't think I have postpartum depression but I could be wrong... any advice or words or anything you be greatly appreciative.