I think my period was 7/18ish. They usually last 4-6days and come around every 28 days. Sometimes due to stress, they are a bit irregular or I will miss a period. Until recently, my boyfriend and I practiced abstinence, so when I missed a period, my mind didn't jump to "am i preggers?" We used a condom the first time we had sex (while i was on my period) I think I missed a period but think I was ovulating around 8/26, which was a day that we fornicated. On that particular occasion, I am sure the condom slipped, but he didn't say anything. There was ejaculate on me, and surrounding areas, and times he had to adjust the condom during the sex. I took a pregnancy test today (because of the missed period around the 10th) but it was negative. I am now worried that on the 26th I could have conceived. However, I am not even positive that my dates (7/18 and 8/10) are correct. Can someone let me know what the likelihood of me being pregnant is, or if at the very least I should be concerned?