Hi there hun, your post was a while ago now. I'm actually starting up a blog for new single parents and came across your post while doing research. OMG I know what you are going through almost exactly! You poor poor woman. No-one seems to know or understand and maybe even remember what it's like to have a new baby after so much physical work carrying and delivering the baby and then all the mental and emotional pressure that follow. When you add to this the fact that you have no-one to help, then the sleepless nights, the guilt, it's almost inconceivable that so many of us get through it and manage to raise healthy, happy human beings... but we do. And you will. I hope I can help.
First of all my advice is to just BREATHE really deep. You need to and deserve to take 3 mins to yourself to breathe and get yourself to place of relative okay-ness. This is if your little one is crying or not. It's hard to leave her but it is likely nothing will happen to a crying baby in 2-3 mins.
Second thing; you need to get help. Which borough/county do you live in? I can look up people to help you in your local area (if you're close enough, I might even come myself).
One of my saving graces was my local children's centres. In lambeth, South London, they have breastfeeding workshops with a registered paediatric nurse. These are a great place to start -- I did because, like you, my son wouldn't stop crying and it turned out he was hungry because he wasn't latching properly and I couldn't tell. They also have home visits with registered therapists for mums who are finding it a lot to deal with psychologically - a friend of mine used them and swore it helped her get through really tough times.
The children's centres themselves run sessions for you and baby to see a health visitor or other health professional and they are full of mums who are seeking help in one way or another so don't be shy or embarrassed. Your HV should be able to point you in the direction of the nearest one and they're usually walking distance. If not, just google search in your county for children's centres.
If you need a hand getting out the house, ask you HV for extra support, I got some from mine and it was gold-dust.
Let me know how else I can help. YOU are the reason I want to start this platform for single parents. There is not enough done to help people doing the hardest job in the world and it's just assumed we'll get on with it because so many of us have struggled through it before (but not without losing a few marbles!) I will offer any support I can, my love, so don't be afraid to DM me on here if poss or on Insta bravenewheart or Twitter ThisBraveNewHeart.
Please please please let us know how you get on.