What can cause bright red/fresh looking bleeding for 2 months every other week almost like clock work?

I had my daughter in 2008 and then my son back in September 2010 then in October 2010 I started on the Depot shot then in April 2011 i went off the shot. then in june of 2011 i started bleeding i thought that it was just my period stating again nothing new. But then about a week later i started bleeding again and ever sense then i have been bleeding every week starting on like a sunday and stopping on a wed. but its not the normal period bleeding that i had before starting the shot. I have never have irregular periods in my life. they always were on the 2nd week of the month even after having my daughter. So i took a pregnancy test and it was neg. so i waited 3 weeks and took another and it was neg. so i need help trying to figure out whats going on. the doctors said its normal but i don't think it is at all normal. So help me please!!!!