Hi Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern...
No intake of Unwanted 72 pill will not cause regular periods in you. In fact
Emergency contraceptive pill or Unwanted 72 is type of medicine which can cause
irregular periods as side effects. As you are previously suffering from
PCOS therefore intake of unwanted 72 pill is not advised to you.
You could use regular birth control pills. They would be helpful in preventing unwanted
pregnancy and also would help in prevention of Irregular periods. It is first priority drug in treatment of PCOS if both
contraception & regularizing of periods is required. However chances of pregnancy after intake of unwanted 72 pills within 30 hours of intercourse is very less.
Therefore you should not stop taking your medicines for treatment of PCOS or irregular periods. Avoid using unwanted 72 in future.
Consult your gynaecologist for starting of regular birth control pills
Hope this information helps