Hallow Dear, 
It seems you have been mis-informed about Norifam.
Norifam is a brand of injectable 
contraceptive that be injected on the first day of your menstrual period (first day of bleeding). 
From your history, it appears that you have taken the injection on the day 2 of your bleeding. This delay may cause failure of 
contraception during first month of the injection. 
However, you had 
unprotected intercourse on day 7 or 8 of the cycle. On these days, the egg is not released as yet, to get fertilized. The egg is released (ovulation) 14 days prior to the next expected menses. The egg has life of 24 hours and the sperms are active for 72 hours. Hence a period of about a week around the day of ovulation is fertile window. So if the menstrual cycle is of 28 days, day 14 would be the day of ovulation and the fertile window would be between, day 10 to day 18 of the cycle. Your sexual intercourse was 2 days before this window. 
You will have your 
menstruation period after Norifam at the regular time. You have some misconception that you get period 3 weeks after Norifam. You will get it at your regular expected time of the cycle. I believe your menstrual cycle would be somewhere around 28-30 days; and you would get menses around that period. 
Considering your history of sexual contact, I do not think you are pregnant. However, if you are in doubt, you may perform 
Beta hCG test on your blood 10 days after the last sexual intercourse. If the values are below 5, you are not pregnant while values above 25 are diagnostic of the 
pregnancy. 
I hope this helps you. 
Dr. Nishikant Shrotri