Hello, Thanks for writing to us. Your chance of pregnancy is EXTREMELY RARE or NIL if you did unprotected sex around expected date of period in regular cycle. Hormonal imbalance and mental stress can make late period for 7-10 days. Other causes are over weight or sudden loss, emotional upset, change in eating pattern, thyroid problem, PCOD etc. Here, I suggest you to await another 3-4 days to get back your period by nature and if you don t get it, you must undergo one USG lower abdomen and hormone test to rule out other underlying causative agent and confirm the diagnosis. Kindly, consult with her local gynecologist and take advice accordingly. She may need to take hormonal pill to induce period. You should control body wt, avoid stress, take healthy low carbohydrate diet with avoidance of fatty food and sleep properly. Be well and take care. Practice safe sex. Good luck.