You should use protection for the first year after your last period. Your period might start up for one month or two after stopping for a few months, in which case you have to start counting and using protection for a year all over again, or you risk getting a "boo-boo baby". I think all that fooling around at a later age can get your hormones revved up again for mother nature to take one last chance. Thats what it felt like to me, anyway!