Do you have a firm diagnosis? Sounds like the oncology tests were inconclusive, no genetic markers for ET or another MPN, just elevated platelets. A bone marrow biopsy might be the next step in getting to the bottom of this. If you have ET, the bone marrow biopsy would show some misshapen megakaryocyte (cells) in the bone marrow. Fatigue is part of ET and other MPNs, but it is also a symptom if many other ailments. So a good diagnosis is important. Best of luck!