What Causes Night Sweats?

Hi, I have been having night sweats for the past 5-8 months. I tested negative for HIV about a week ago, and I haven t had an at-risk incident since before the night sweats, so I m well beyond the window for HIV to be doorman. I have a doctor s appointment next week, and I just want to know what questions I should be asking for them to get to the heart of this. I m worried about things like cancer (I ve been reading forums/information online, needless to say) and I m afraid of coming off as a hypochondriac.