What Do Recurring Nausea, Hot Flashes And Constant Low Grade Fever Suggest?

For 5 months now I have had nausea without vomiting and it comes up at any time. I went to the doctors and had tests and the tests came back completely normal and had been the healthiest they have ever seen someone at the age of 17 at the time. Now I am 18. They could not figure out what was causing it and sent me home. The nausea is still going on, along with hot flashes, and a constant fever of 99-99.9