Could The Delayed Periods Be Due To Stress Or Unprotected Sex?

My last period was a month ago today, in the middle of that period i had unprotected sex with my boyfriend where he pulled out before ejaculating, he is positive that he didnt ejaculate inside me and tells me not to worry. I have been worrying though, a very lot for the past 2 and a half weeks, I don't believe I have had any symptoms of pregnancy, but I am still worrying alot, and am very stressed out. I have been having a few period pains, but am just having more discharge. I'm worried, what are the chances that I am pregnant? or is it just stress that could be delaying my period? Thankyou