Unprotected sex

I had unprotected sex tonight and only afterwards realised I hadn't started my new pill as it needs to start first day of period. So have been without for about 1/2 weeks. I quickly doubled up on the old pill but I am so stressed. I'm on day 21 of my cycle, (usually 29 day cycle) what are the chances of pregnancy?? will I be okay to just take the pill again or should I get checked?