Hi insomnimum and a big welcome. It does definitely get easier. This bit is so hard and my advice echos the others. Mine were in babygrows until they were 6 months, round the clock, changed when sicked on or pooed on. I had lovely clothing gifts but no time to dress them up and oooh and aaahhh. After this crazy bit settles slightly you'll start feeling a little more human.
A helpful HV will definitely come to you. If she won't and you want her to, complain, make a fuss or change surgery. I didn't go to the baby clinics either. Once I got myself there I wasn't allowed to take my buggy past the main doors. The girls on reception were great and would have held a baby but you are fighting the clock with feed times and even waiting to be seen can take ages. With what you managed today you should feel very proud of yourself, and I so wished you'd created merry hell at the "we're not seeing anymore today". These are the same professionals that tell us we must ask for help if we feel we need it!!!!!
Sleep is chronic. I couldn't get mine to feed around the same time day or night and you just feel like you can do nothing else. However, try to be kind to yourself. Tell yourself if you stay in all day it may as well be nice. Mug of tea, packet of biscuits, daytime telly, feed, change, wind, feed, change, wind, snooze if you manage. When you have more energy you can manipulate the schedule a bit to create a showertime! If they can feed together then this will come quicker, Mars always said if one fed, she fed the other, if one needed changed she changed the other.
Try to ride out the crying. Mine cried a lot and didn't just feed and sleep. Sometimes you have to walk away, leaving them both screaming, just to pee, make tea, breathe, cry etc. This is totally fine, it won't hurt them a bit and when they are older won't remember a thing about it.
I had days I felt like I could do anything (used to have one in the double buggy with my dd who was 3, one in a sling and walk like a packhorse a few miles along the road to a gym class for dd. Feed, change, give dd lunch and walk back again. It was heaven to get out, hard, sweaty work but heaven to feel fresh air on my face), then I had other days when I shouted and cried and felt like I was a total failure. Its all normal.
Now you've found us, don't lose us. We're here good or bad. Good luck sweetheart.