Should I give the baby up for adoption?

Long story short I'm 21 weeks pregnant, too late to have an abortion. I have a 4 year old daughter and am with her father we've been together for 5 years. We have a terrible relationship, and when I got pregnant I stupidly thought that this would make him change his ways. I don't like being a mum, I resent the daughter I already have at times because she is hard work. I do love her but I know I haven't been a good mum to her and we're not a happy family. I should have had an abortion but I didn't and now I'm thinking about giving this baby up for adoption. I am so sick all the time and my depression is even worse than normal since being pregnant, I'm miserable and just want all this over. My partner won't help me at all he is nearly as dependent as our daughter and I know he won't want us to give up the baby but he won't lift a finger to help and I can't do it on my own again. I feel so miserable, please give me some advice on what to do. Btw I live in Qld so where do I go to look into adoption?