Hello,
If you are apprehensive regarding the status of your pregnancy you can get it checked. Most home pregnancy tests that check urine beta-HCG are sensitive to 20-25 mIU/ml of HCG. The test can be positive anywhere from about 2-3 days prior to a missed menses to 4-5 days after, but usually it should be done 7-10 days past your missed period.
Otherwise you can get a serum HCG also done which is more specific than urine pregnancy test.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
I think if you took a morning after pill, it is normal to have an abnormal cycle afterward. However, your cycle was abnormal before you took it. If you weren't having a period, you weren't ovulating so it would be unusual that you all of a sudden ovulated the one time you had sex. I would say it is very doubtful that you are pregnant. Remember, you hit your body with a hefty dose of hormones with the morning after pill.
I personally would see your doctor to discuss why you hadn't had a period in years. that is very unusual at your age. good luck