Hi there. 
I have understood your concern and I will suggest you the best possible treatment options.
1. First of all please do not panic.
2. As per your history, if you had your periods after the episode  of protected sex act; you were not pregnant in that cycle.
3. Now also , you have 2 weeks delayed period. 
And you did not have sex act in this cycle. So there is no question of getting 
pregnancy.
4. If you are concerned that you were pregnant in the last cycle in which you had  delayed period and  heavy bleeding, at present there is no way to detect it as on now.
5. I will suggest you to get USG done to rule out 
PCOS as a cause of your delayed periods.
Also, please get proper sex counseling done, proper use of suitable 
contraceptive method will help you prevent unwanted pregnancy . 
In my opinion use low dose birth control pills will helps you to prevent the pregnancy and have regular cycles.
I hope this answer helps you.
Thanks.
Dr. Purushottam Neurgaonkar