Nausea and headaches

Yes to both, although my situation is a bit different (high ostomy).

Believe it or not, dehydration can cause nausea and the headache. I really didn't want to believe my surgeons office but I think they are right. Add some electrolyte drink to your daily diet.

Agreed. Sounds like dehydration. Be sure not to drink something with a lot of sugar (e.g. gatorade). I drink vitalyte, but I think my problem is not as bad as yours (mostly just in the heat of the summer). Others use oral rehydration solutions (e.g. pedialyte, but you can also make your own). If you're having these problems, it's better to drink an electrolyte solution than plain water (which strips electrolytes).