Hi. Here is how our core body temp works. It has a base level and it begins to rise before we ovulate. Not much. Like a degree. But if you chart it, you see it clearly happen. It's biology. As your period is about to begin, it dips back down a degree to your baseline. If it does not dip back down, that is a sign of pregnancy. I tracked my cycle this way for 3 years and it followed this pattern the entire time. That doesn't sound like what you are describing. Hormones can fluctuate and give a hot flash. Ovulating and then either pregnancy or getting ready to start your period will fluctuate your hormones and we can get a hot flash then. However, a high fever? Probably not. maybe you caught a virus? Is this just a one cycle thing that happened?
Maybe you got colds or the flu? You best have yourself checked by the doctor. Are you trying to conceive and taking any medications for this? It might also be a side effect. Can you give us an update?