I don't really know what to say, but I don't want to stay quiet as I am a mother myself and glas a child, grew up under an extremely abusive situation.
I am so sorry that you feel the way you do and it really does sound like a horrible and painful situation to be in if you are finding parenting challenging. I do appreciate that being a mother is a difficult role - I have found the role of the mum being the most challenging, though thankfully I would never swap that for anything else - but with motherhood comes the responsibility of looking after our children who we have brought into this world. I hope that your children are okay as well. And I hope that you find that things have calmed down for you once the youngest has left home.