18 months off depo!!

Tristina
Last month was 18 months I have been off the depo shot. & I had a STRANGE encounter with bleeding, I started bleeding in the beginning of the month until the end... I went to the doctor & she said it was old blood coming from my uterus... Could this be my body FINALLY flushing all the depo out?! 
I know I sound crazy, but there should have been quite a few times I should have been pregnant from my boyfriend. But I just cholked it up to my depo was not fully flushed...
Since then I have had no bleeding, except my period. & I also began charting periods. 
Opinions?