Hi OP
Poor you. I think the mental health side of being sleep deprived is really under estimated.
I have been where you are. Upon every 90 month or so to feed and I felt like I was only getting back to sleep (takes me a while) when I woke up next. I started getting so anxious about planning to do anything in the day, as I knew I'd probably be tired and miss the opportunity for a nap, so I became a bit of a recluse and didnt enjoy my maternity leave. I only stuck it out for 7 months before I sleep trained. We got someone in to help because nothing I tried worked.
I could write a massive post on this but we essentially did the disappearing chair method where we sat beside her, patted her, picked her up if the screaming got awful, and over the course of 10 nights moved it gradually further away til it was out thr door. First night every wake up waited 3 min to see if she self settled then the next night 4 min then worked up to 10. She woke up once for a feed thr first night (which I was happy to do and advised to do it since she was only 7 months - but only between 1 and 3am or something) and didnt after that. So was sleeping through on second night. To be honest I wouldnt think she needs feeding in the night at 10 months it's just habit. If she had woken up more, we would have waited the number of minutes and gone and sat with her til she fell asleep again.
This completely changed her behaviour in the day. She was much happier and ate and drank a lot more as she wasnt getting 90pc of her calories during the night. Ans naoowe consistently.
You will need your partners support though, I wasnt emotionally strong enough to do it myself. You really need two of you doing it at the same time to support each other. In fact the sleep trainer advised that my husband did the first 3 nights then I do the next 2 then we alternate every night. So that firstly the first few nights are a bit easier as they get more distressed if they can see the mum and want her milk but cant have it. With dad they accept a bit quicker that they arent going to get fed. Also it ensures they dont get into another bad habit of only going to bed for one parent.
I still breastfed her in the day at set times and by the time she was one did it first thing in the morning and last thing at night. She was a baby who really really needed a strict routine.
If your partner has any holiday over christmas I'd work out a plan of how to tackle this together. It normally works within 3 or 4 nights and a few awful nights is much better than months of awful sleep.
I also had another daughter that woke once a night to feed and we sleep trained her by accident at 8 months as I had a bad back, and my husband got up with her and tried to settle her before coming to get me (as he had to help me sit up and put her back in bed, so it was easier for him) and this was much easier but she was not as strong willed as the younger one who was an awful sleeper and resisted all my gentle methods!
One thing I found though is that the sleep anxiety for me lasted a lot longer than I thought. It wasnt til she was about 18 months old and I realised she had been sleeping well for longer than she had been sleeping badly, that my brain kind of let itself relax properly and I didnt constantly feel like I had to be half listening out for her, or start panicking every time i heard her cough or cry or anything. Also I had a massive hormone crash, with symptoms like headaches etc when she started sleeping through as it was so sudden - my body was used to waking 7 times a night and feeding so probably thought I was looking after newborn twins or something, then went to feeding a handful of times in the day only and it made me feel quite poor for a couple of months while I adjusted. I might have been unlucky here as I havent heard of that happening to anyone else though!