What Causes Delayed Periods After Coming Off From Contraceptive Pills?

Hi, I had gone off Loestrin 24 about 3 or 4 months ago in February. The first three periods I got OFF the pill were regular-Feb. 14, March 18, April 18! Since then, I haven't had a period and am over 2 months late! I am having unprotected sex but went to the doctor who did a urinary test and told me I wasn't pregnant. What's going on-could this be from going off the pill evne though those periods were regular? Or could I be pregnant still?