Nightsweats can be a sign of inflammation or infection. I had bad nightsweats for several months after my surgeries. I never had them associated with a fever, and infection was ruled out. I've also had them associated with pouchitis. This could just be your body's reaction to the recent surgery and/or side effect from the meds, and it might improve over the next few weeks, but I agree with dtmack that an infection should be ruled out, especially since you did have surgery quite recently and as we all know, infection can be a complication.