3 months ago I had Nausea for 2 weeks. No diahrea or fever. Blood/stool test negative for everything. Now I have only nausea again. What could be?

Nausea. This can result from central nervous system issues, problems in the semicircular canals, GI issues, pregnancy and a wide variety of other issues. If this continues, seeing a good diagnostician (Family practitioner or general internist) might be a way to start to evaluate this. Good luck.