Is It Normal To Have Period For An Extended Time After Getting Off Depo Shot?

hi i am a 25 year old female i been off depo shot since november of 2009 and every since then i been haveing a 2 week period untile last month my last period was march 20th 2011, my period lenth is 32 days and i only bleed for 7 days and it was really light it normally be heavy then this month i get brownish discharge dnont no discharge or blood come out when i use the restroom just on the tissue and its been like that for 4 days could i be pregnant please help!!!