Hi Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern..
No chances of pregnancy after taking postinor 2 are very less. Postinor 2 is an
emergency contraceptive pill & This pill works by preventing
implantation of fertilized egg on the wall of uterus. It is 95% successful if taken within 24 hours of having sex.
As you have taken the emergency contraceptive pill within 12 hours of intercourse, you should now relax as possibility of pregnancy is very less in you.
Use condom or regular contraceptive pill as method of
contraception in future. As you have history of
irregular periods intake of postinor 2 is not advised to you.
Emergency contraception should is less effective than regular methods of contraception & also it has greater side effects too. Regular taking emergency contraceptive pills can cause problems like irregular periods, ovarian hyper-stimulation syndrome & even
infertility.
For more queries consult a gynaecologist
Hope this information helps