im worried if i might be pregnant

My boyfriend and I had sex 3 days before my normal period date.. and he came in me and we werent using any protection. I'm worried because we didnt take any plan b either.. im 3 days late, is there a posibility I might be pregnant? 
PS. I read online that if you have unprotected sex before your period means you are the farthest from ovulation, and the chances are really low. 
Help?!