PCOS can cause symptoms of abnormal menstrual bleeding. (multiple cysts on or of the ovaries) But it seems that you are definitely experiencing secondary amenorrhea ( you used to have a regular period but then it stopped for at least three months.
Are you sure that you aren't pregnant?
Could the lack of menstruation be caused by breastfeeding?
Other causes could include:
Hormonal problems
Low body weight
Premature ovarian failure
How to treat amenorrhea?
Treatment for amenorrhea depends on the underlying cause. Sometimes lifestyle changes can help if weight, stress, or physical activity is causing the amenorrhea. Other times medications and oral contraceptives can help the problem. For more information, talk to your doctor.