I think much of what you describe is actually very normal and common for mothers to feel at this stage - even when they don't have postnatal depression. Its just not that openly acknowledged because it feels like its not okay to admit it.
My daughter slept through for 6h for the very first time at 5 months. However, that was unusual
Things did get better once we started regularly getting 4h blocks of sleep regularly. It's a gruelling slog, in those first months.
The little squishes don't exactly give much back either. Yes, they like to snuggle on you to sleep. They like milk. You might get the odd smile. Though at 5 months, I think the only thing my daughter smiled at were my boobs. This was one of the main reasons I kept breastfeeding.
It feels like they spend a lot of time yelling at you, as they realise how they can't move and can't communicate, but start knowing that they want things. At 5 months, they start getting bored, and knowing it.
I do remember feeling like many days I cared for my daughter out of duty rather than with affection - and felt guilty as heck about it!
So how do you get through this phase?
Are you going to any mum and baby groups? Good ones with sensible mums will have some open discussion of all this, so you don't have to feel so alienated by your family's different sentiments. It's easy to be all awe and gushing affection when you get to give the baby back and are getting full nights sleep.
Also, lots of walks with the pushchair: it's fresh air and exercise for you (good for mental health) and less boring for the baby. More importantly, it gives you physical and mental space, getting the baby off you - if they cry it never feels as loud outside either.
You clearly do love your child. You probably will like her when she has a personality that is more obvious that a milk and cuddle obsession. If there was no bond, she wouldn't want to cling onto you! Don't let a fear that postnatal depression has had long lasting impacts colour too much the simple situation that babies are hard work. It IS hard to like something that just takes and demands, but it will get easier.