Have you had a bone marrow biopsy to be sure that what you’re dealing with is ET and not another myeloproliferative issue such as MF or PCV? You may want a second opinion. My Dr originally diagnosed me with ET based on blood work, but similarly Hydroxurea was not keeping my platelets down. I sought a second opinion and was referred for bone marrow biopsy, I have Myelofibrosis, not ET. This is from what I understand a common misdiagnosis.