I Just Had Surgery To Remove My Gallbladder Yesterday And

I just had surgery to remove my gallbladder yesterday and today I am having extreme dry mouth. I have drank 5 bottles of water and alot of juice, but nothing cures it. I also not having diarrhea so i figure im not dehydrated. Its getting to the point where i cant even eat because my mouth is so dry, it prevents me from swallowing.
I really need to know why this is happening and how to stop it.
I was prescribed percoset and phenergan if that helps.
Thank yoi in advanve