I had a GI doctor once who used to say "if you are going to be sick whether you eat toast or a steak, then why not eat the steak?"
Basically, you have to eat. You should be on a soft food diet right now. Here is a link to what a soft food diet is: https://my.clevelandclinic.org...l-soft-diet-overview
Start slow and slowly add fiber and less soft things to your diet. Certain things will make you gassy or uncomfortable, just like when you were sick: onions, garlic, cabbage, mushrooms, corn, spicy food, etc. Stay away from those for now.
And definitely drink lots of water and electrolytes. I drink Vitamin Water Zero, and G2 (gatorade with less sugar)- those were suggested by Cleveland Clinic. All the electrolyte tabs and powders are good too.
Just hang in there. It eventually gets better. I'm almost 10 years post take-down and I can eat anything. You just need to learn your body.
Also, while talking to the Jpouch community is great and very helpful, you need to talk to your doctor too. If you aren't feeling well, they are the only ones who can help you and who can figure out if something is wrong. If your surgeon doesn't take your insurance, you need him to refer you to some other surgeons and figure out who does. GI doctors are great, but in the year or two post take-down, you need to be followed by a surgeon.