I also heard about some medicines and a ton of other strategies, like diaphragmatic breathing or drinking herbal tea, that people use to help with regurgitation: https://www.verywellhealth.com/regurgitation-7485353. Don't know what you've tried at this point, have you done antacids, H2 blockers, and PPIs? Also I read that quitting smoking might help.

If worse comes to worst, maybe you can get nutrition through an IV temporarily; definitely NOT a good option because I think I heard there is a risk of not being able to wean off it and there are other possible serious/life-threatening complications like sepsis and liver damage, but it's there if you need it. I was considering it a few years ago when I was so backed up I could barely eat. Thankfully I found a breakthrough and never had to resort to that, but at least I knew the option existed in case of an emergency and I wasn't going to starve. Other options are subcutaneous fluids (which are safer than the IV route), G-tubes, J-tubes, nasal tubes. I just cringe at suggesting this stuff because I'm all about waiting it out as much as possible and not damaging my body by hammering it with artificial stuff to get it to function before I'm able to find out what the problem is and address it. I was prescribed Linzess a while ago for my severe constipation but I'd heard that it can permanently mess some people up, so I decided to hold on and look for better solutions and lo and behold I'm noticing signs that my gut hasn't forgotten how to work.

If you manage to start drinking again but can't eat, maybe you can do Pedialyte or Ensure to get nutrition. God Bless and I hope you find some answers!