Hello :)

I've been on Depo for the last year, I've deceded to come off of it and did not get my November 15 shot.  It is now December 20, and I still don't have a regular cycle, which is normal as I've been on/off Depo for the last several years and I usually don't have a period for the first few months after coming off of it.  I have not been sexually active, but plan to become sexually active soon.  I'd like to switch to the pill, and I am wondering when I should start the pill pack, as I still don't have a regular cycle.  Would I start from the first day of my last known period?  I.e. January 5 was the first day of my last known period - so do I have to wait until the 5th of the next month (which would be Jan 2013)?  Or can I start as early as tomorrow, Dec 21? 

I plan to ask my doc all these questions when I go to get the prescription, but I am wondering if anyone knows/has experience with this so that I can plan my timing...any helpful input would be appreciated!

Thank you!!