You may want to consult with your GYN. I'm not sure about he canker sores and the swollen gums
Sometimes periods can get delayed. A normal menstrual cycle occurs every 21-35 days with menstruation for 2-7 days.
If there is a history of any unprotected intercourse then pregnancy can be thought of. Other than that, High level of stress, cholesterol, hormonal imbalance, chain smoking, dramatic changes in your life style may be some of the common causes of your delayed periods.
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.