So, I had unprotected sex on June 26th and July 2nd. My period was supposed to start around July 8th, however, it was 7 days late- coming on the 14th. I am usually on time and it lasts 5-6 days. This time it only lasted 2 and after it ended I had a couple days of dark brown blood in my underwear. It wasn't very much but it was enough to get me thinking. I have also been having headaches, nausea, and I have been quite tired at random moments. I have thrown up 3-4 times in the last week. My friends think I may be pregnant, however, I feel he symptoms have been happening too soon and that they may be in my head or maybe a stomach bug of some sort. Any thoughts?