I think every new mother goes through the stage you've just explained.
I currently (even though my DS is almost a year old) am still going through all of this.
I still bf which means it's still falling all onto me majority of the time, I get mastitis almost every month due to hormone imbalances, which I DO NOT wish Apon anyone! Mastitis is very much the devil!
I can't cope with the whole 'being a new mum and losing who I am outside of mummy'.
I love my son dearly and wouldn't change him or having him for anything in the world, but sometimes (99% of the time for myself .) it is overwhelming being responsible for a little human, who although you carried for 9 months, you don't know and have to learn to understand etc.
do not feel like you are alone, we are all here, we have all either been there and or are currently going through it right now.
And with every new milestone (not sure what else to call it) it gets a little bit harder, at least for my it has. As things change, the amount of stress you have will too, and even though it's a hard and terrifying transaction you'll still find yourself missing it as they get older!!
PM if you'd like to chat lovely
Edit: it gets easier not harder! Haha whoops