Well I think you are being a good mum. Being a good mum is about trying to fix problems and do your best. And what you have been through sounds really difficult. You have to give it time.
I had ptsd after my ds birth and could not cope. Things are much much better. I'm a single parent now and do virtually everything for him. But that has been two years. It helps to focus on what is going well, the good things that happen each day, not the failures.
How is it when she is at home with you?
Are you having therapy? It helped me having my space to talk freely. I also go to a support group for parents with various issues and it really helps to spend time with other people who are not loving every minute of parenthood, perhaps because they are depressed or their child has extra needs.