I got off birth control after taking it for 4 years. had my last period on it but haven't gotten another period for almost 2 months after that. why?

Pills? : I assume by birth control you mean birth control pills? Some women can have a very short delay in return to regular menstruation. Most commonly, however, stopping birth control pills does not cause infertility or menstrual cessation, unless, of course, maybe you had problems with a regular cycle before you got on the birth control? If no period After three total months, see your doctor

Birth control pill: Depending upon the woman, the type of pill, and the length of time you have been taking it, it may take anywhere from several weeks to several months before hormone levels regulate and allow regular menstruation to resume. In addition, if your periods were irregular before taking the pill, your periods may continue to be irregular after stopping the pill. Always a good thing to talk to your doctor