Separation? Husband issues.

In one of our common, daily discussions I asked my husband why he gets upset all the time and I couldn't believe that his answer was "we're just too different and we don't click, the things you say are irritating ". I haven't been a model wife and we live with his mom, things have been just been accumulating from day one. But I'm shocked, sad, and I just want to leave him, we have a two year old son and I'm pregnant and any thoughts of separation make me very sad, specially for my children. Not sure what to do. Am I overreacting?