A GP is not going to have any answers for you. They do not specialize in blood cancers. I suggest you find a doctor whose specialty is Leukemia. Blood tests can identify high platelet counts and abnormal white or red blood cells. For instance, the ratio of white cells to red blood cells or the size of the blood cell may be too large or too small. In my case, I have a lot of white cells that are "immature". There is a blood smear test that looks at the most common gene mutations. I suspect that is the test they used to identify your JAK2 mutation. I don't know where you live but there must be a Leukemia group near you that you can call for a consultation. My bet is they'll recommend a bone marrow procedure and a molecular panel. Good luck.