I was on depo for about a year (maybe not quite) and i came off it to get preggas with #2 but it took 14 months to regulate AF, 12 months to even get AF!!!
I too was eager to start so i did chart but really just confussed myself even more as AF does play a BIG part in charting!, i did end up getting pregnant before AF had even come (wouldve been the 2 weeks before AF was due seen as i all of a sudden ovulated!) but i misscarried and after disscussing with docs and having scans it was more than likely because there was too much build up in there from having no AF for so long and bubs couldnt hold on

so it really is best to get AF...no harm in charting though i guess..
You could maybe talk to your doc about getting Provera to reverse it??? not sure it thats possible but i remember being told that it can take from 3 months - 2 years!! different for everyone though..
good luck