How Should Amenorrhea Since Discontinuing Birth Control Be Treated?

Hi! I have not had my period since November. I am obese and I stopped my birth control around that time. I have taken 3 pregnancy tests and they all came up negative. I am just wondering if you could tell me if it's due to the cancellation of the birth control or could it be something else? I have also had problems with my period since I was 15...I am now 30. Thank you for your time!