What Causes Prolonged Red/brown Vaginal Spotting While On Depo Shot?

Yes i started taking the depo shot 6 weeks after i had my son in april i had my period and the shot made it go away and didnt have my period in may and i got my period june 6th it was a red spot it has been spotting for 8 days but it went from red to brownish now its 9th day and its red again is it normal to have your period for 9 days also if you get your period when on the depo can you still get pregnant