M.B.
Hi K.. These things can take a week to get over, so it doesn't sound to weird to me. Mainly, I wanted to reply that I went through something similar with my daughter when we were breastfeeding and supplementing with formula. When she had the stomach bug in the fall, she would only keep down breastmilk too. That's sometimes just because the breastmilk is so much easier for them to digest, not necessarily because the formula is bad for them. If she is not dehydrated (still peeing and active), she's probably still recovering and doing okay.
Also, PLEASE don't dilute formula. That is very hard on the baby's system because it's a delicate balance of electrolites and everything they need. It can really hurt them to give them too much water--not to mention that they aren't getting nutrients. Pedialite is much better than watered down formula. I asked my sister, who is a doctor, about this when my baby girl was vomiting.
Hope you all feel better very soon!