I had been taking the Yaz birth control pill for 4 months, and at the end of my last pill pack I didn't start a new pack.  I got my period at the appropriate time of the last pill pack, but it was lighter and shorter than usual.  During this time that I was not on the pill I was not sexually active.  However, it has been six weeks that I've been off the pill (and not sexually active), but I still haven't gotten my next period.  I've taken two pregnancy tests which were negative, just in case.  I've heard that the pill can affect periods like this after it is no longer taken.  My question is: can/should I start taking the pill again now (and become sexually active), and will I be protected from pregnancy and get my period back?