I have mild itp & for last 18 mos. i've had intermittent sharp pain in luq just behind last rib. ct scan and md exam shows no abnormality. what to do?

Probably not the ITP: Itp is not associated with pain (anywhere). I assume you are worried about your spleen, but, again, that should not be an issue with this diagnosis. A ct scan would have detected anatomical abnormalities in the area you describe. Sometimes all we can do is rule out the big bad diagnoses and keep monitoring the nagging symptoms for a while to make sure they don't become worse.