Sounds like during your operation they didn't give you enough fluids, so you're making up for it now. After one of my ops, when I came round, my mouth felt like I'd been buried in a desert for a week. I was so unbelievably dehydrated.
So don't worry about it, and besides, you're supposed to be drinking at least 2 litres a day. So I doubt it will be hurting you.
