What Causes Missed Periods After Stopping Birth Control Pill?

HI, Im 25 years old and was on birth control since age 17. I went off the pill in july 2014 and still haven t had a period. Ive taken pregnancy test and Im not pg........Ive spoken to my ob/gyn a couple months ago and she sd that this can happen.....still not having a period is making me nervous...will this mean Im infertile?