I give up being a mother..

So I'm at my wit's end now, I feel awful even writing this, I'm a 27 year old single mum, aged 7, 6, 4 and 3. I think my eldest suffers ADHD, he's currently on the waiting list to be assessed, he has severe anger issues, to the point I'm scared to leave him alone with the other children as he always hits them, I have to segregate him and keep him with his grandfather. I'm just at a point where I've given up being a mother, none of my kids respect me, they tell me to shut up, they call me stupid, dummy, they trash the house and not in a normal way, as in they purposely open cereal and pour it all down the stairs, they pour drink in my car, I honestly just give my all to them and they just throw it in my face, what's the point of even being here I dont get it