What Causes Recurring Petechiae And Bruises On Arms?

Hi. Petechiae comes out on my arms nearly every week and also i bruise very easily, sometimes I'll see a bruise on my skin and can't remember if I've gotten hit and my body feels pretty drained at time. The last time i visited the doctor my blood count was low, i dont no the cause. But i haven't visited a doctor concerning the petechiae. Have any idea what is wrong with me?