Well, it depends, but maybe what it is is that they gave you fluids, and now you're dehydrated? Maybe try drinking more and see if that helps? Otherwise, I don't really know, sorry.
I drink a 1/2 gallon of water every day and that does not seem to help. My surgery was I had two diverticulum rupture and had 12 inches of my colon removed...it was hell.
IV fluids usually consist of water and salt. 1/2 gallon of water is the minimum recommended so I would try increasing this. Also you might want to try adding more salt to your diet.
Tropical, that bag the docs/nurses in the hospital used could have contained a variety of different things including antibiotics. Why don't you call your doc and ask to be seen. That's typically the best choice after having had surgery and subsequently not feeling so great and having 12 inches of your colon can change a variety of things.
I garee with CalGal on this. Saline is normally salt, water and glucose, but they can add anything you need to it. If you are having a lot of loose BM's due to the surgery you may be dehydrated and you need more than just water to get re-hydrated. When we become dehydrated we lose electrolytes, and this can make us feel lousy. Drink water, orange juice, eat a banana every day and drink Gatorade diluted with water. These things replace your electrolytes, and you will feel a difference. I would definitely talk to your doctor about this, there may be a clue in the IV bag that could help them to help you now. Good luck and take care.