I've been on depo-provera since may 2014, and my next shot is january 2015. today i had bad back pain and some brown and red spotting. what is it ? my period?

Break-through bleed: Hi, It seems that you keeping up with your Depo-Provera schedule. As with all Depo-Provera users, the possibility of irregular bleeding is always there particularly as you get close to the time when you need another shot. Also the levels of Progesterone fall over the 90 days and there can be some break-through bleeding. This is what I believe is happening at this time.