Please see your doctor. I'm not a doctor, but "post-partum depression" comes to mind. Your doctor will have options to present to you and knows which option may benefit you most.
Well, you do sound off your old balance, for sure. I once saw a movie in which the husband and wife were having an argument, and he said "Where's the happy girl I married???" It rang true for me thinking of my sister and her husband, she's mad all the time and they used to be cute and fun. I think in her case, it comes from worries about money, and the clash of certain parts of their personalities that are not at their best when each of them is worried about money. When they were dating, they had no worries, each was working, they were pretty carefree and living adult lives where they were autonomous and had few strains. Then marriage and babies, and suddenly she couldn't work because they had two kids and it was less expensive for her to stay home to take care of them instead of work, and so they had less money and less time to have all that carefree fun and think only of themselves. Then he quit his lucrative job and started his own business, and the business didn't make much money, and they are living on savings, and she's really easy to upset and he's annoying and critical to her. Not a good scene.
Why not talk to your doc and get your hormones checked, and then try to get some respite care for yourself, someone to watch the kid once a week so you can just go to the mall and walk around, or get a bath, or read a book. It might help a lot.