Hello, I Always Had A Regular Period In Every Months.

Hello,
I always had a regular period in every months. Last month it happened on 15th of July but this current month I am not getting any symptoms of period and it is already 23rd of August. I had sex for three times over 6 months and I took pills immediately. Last time I had sex on July 6th to 10 and my period occurred regularly on that month (15th July). So, is there any chance to get pregnant? I am really very tensed about this matter. Please answer as soon as possible

Thank you