I agree with nessap. Everyone's body is different after getting off birth control. You need to give your body time to readjust to going back to normal. If you really are concerned, I say go to your doctor. But if you had unprotected sex since being off birth control there is always a possibility of getting pregnant, so talk to your doctor and take a test while you're there, but I'm sure once you talk to your doctor, they may suggest it anyway.
Take a test to be sure. Everyone's body reacts differently after getting off birth control. Sometimes it can also be gapping if you had irregular periods before birth control