How quickly can a pregnancy be detected by a blood test. I had my period on 17 Octber 2011 and shortly after that went on the injecting. On 22 October, the same day as I had the injection I had sex. Since 13 November I had have light spotting and cramping. What are the chances that I could be pregnant

If you believe you may be pregnant, then you should get tested. It may simply be a side effect of taking a medication, but pregnancy shows itself in many ways.