Hi, On August 25 I Had My Period And On

Hi, on August 25 I had my period and on September 23 I had unprotected sex but he did not finish inside me. It is October 4, and still no period. I have very slight cramps very seldom times, no headaches, no fatigue, no food cravings, and my breasts are not tender. I have been feeling pretty normal but no cycle!! Could it be the stress or am I pregnant? Do you think I was fertile the day I had sex? What are the chances of me being pregnant? I am 17 years old by the way and today (October4) I had green stool.