Water is making my stomach hurt.

What White Dove says about hunger not being an accurate barometer yet.

You cannot drink slowly enough.  After one normal swallow that hurt,  I had to use shot-glass sized cups to drink from to keep me from drinking too fast.  Ok now, but a first had to re-train.  Eat based on measurement and then wait 4 hours (what my surgeon recommended****il you eat again.  Do not eat until you feel full - stop at or before the measurement you are given. 

I found that when my pouch is full, I get the sniffles.  So now, when my nose runs, I quit eating.  Some people belch, others hiccup, more get the sniffles.  

Watch for your High Level Alarm (HLA) and when it appears, stop eating!

I also found that room temp water or hot teas were easiest on my pouch.  It was many years before I could do very cold liquids.

YMMV!

I'm 12 days and am finding the same to be true for me as well. I love water and hate artificially sweetened anything (pre-op I'd, years ago, given up all soda and juices). I only drank water, coconu****er, coffee, and wine. But, for now, I've given up. I drink watered down G2 Gatorade or watered down crystal lite or watered down sugar free cranberry juice. Plain water just hurts. I hope this passes as I prefer plain or lemon water. I have no advice but just thought I'd let you know you're not alone. I'm in the same boat. I'm going to take the advice above and try some hot tea.