Why Is Procrit Prescribed And Its Side Effects?

I was diagnosed with E.T, 5 yrs ago.Carefully monitored, every 3 wks with my hematologists. I am receiving Procrit shots most of the time. Can you explain the benefits or the implications that this is a sign of my condition not getting better. I do not understand, only that this brings up the hemaglobin levels. My concern is that the do not stay up and the platelet counts remain high.