I started bleeding on 11of sep I had sex on 17sep...

Dear Customer
Welcome, and thank you for trusting us
Regarding what you mentioned, the pregnancy will take place when the sexual intercourse take place within the fertile days of the menstrual cycle.
The fertile days are 12 to 15 days from the start of the menstrual bleeding of the previous cycle, which us is close to the day of ovulation (14th day of the menstrual cycle ).
The history of the sexual intercourse  at the 7th day of the menstrual cycle carries a low risk of getting pregnant but you have to use an emergency contraceptive pills which are effective within the first 3 days of the cycle in order to be safe.
Dear customer, we advise you to visit the gynecologist doctor so that the doctor could do a full clinical evaluation of your case then he will manage it accordingly.
  Stay well.   
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Kind Regards

Dear Customer
you are Welcome,
Kind Regards

Dear customer 
you have a history of sexual intercourse on your 7th day of menstural cycle , so the chance of having pregnancy is nearly zero .
Kind regards