Hi Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern...
No chances of pregnancy are very less after intake of postinor 2 following 
unprotected intercourse. Actually postinor 2 is an 
emergency contraceptive pill & prevents pregnancy by inhibiting 
implantation of fertilized egg on to uterus. An emergency contraceptive is 95% effective, if it is taken within 24 hours of sex.
As you have taken postinor 2 within 24 hours of sexual intercourse, you should relax now. There are only 5% chances of pregnancy in you. Your next periods may also be delayed due to action of postinor 2. 
An emergency contraceptive like postinor 2 should not be used as regular method of 
contraception. Regular intake of emergency contraceptive pill could cause irregular & delayed periods, ovarian hyper-stimulation syndrome & other harmful effects including 
infertility. Next time use regular contraceptive pill or condoms for prevention of unwanted pregnancy.
Refer to your gynaecologist
Hope this information helps