Oh @Needadvice1996 I'll just pick out some parts of your OP
I admit was entirely my fault... we stayed out later which was out of DD’s routine So the 2 of you, both parents, went out and both had a good time with friends. But it is entirely your fault?
It isn't. Every baby has its routine changed and that is part and parcel of them growing.
I think is caused by having PND. I am so sorry you expereinced that.
Partner insisted DD did not need the bath and to just have a bottle and go to bed...[I said that] if she had the bath it would have settled her, I admit now this is wrong. Why were you wrong? She didn't settle. She might have had she had her usual bedtime routine. You could be right!
I think my anxiety almost feels like it needs that structure of routine. I did raise my voice and I can understand why he was annoyed. You seem to do alot of understanding, does he ever? Did he understand your PND?
He showed me the baby monitor to show DD was asleep and then grabbed my head and whacked me 3 times with the baby monitor. So your response to being stressed was that you raised your voice. His repsonse to that was to hit you? And you apologised to him... for what ^forcing him to hit you, with an object?
I did apologise for what I had done and partner admitted too he shouldn’t have hit me, but then said he was provoked to do so? Is this ever okay? You apologised because you were sacred. His apology blames you for making him do it. That is never OK. Ever. And his violence is escalating, from a push to battery.
I hope you have real life supprt. You need to tell someone what he did and make sur that yuou and your daughter are safe.
Start putting yourself first. He is dangerous to you!