wishful thinking

I know this is probably impossible, but has anyone been or know of anyone who got pregnant on the depo shot ??? I've gotten my second job on July 13th. lately I've been feeling sick, light headed with headaches, sooooo tired & have been cramping. ALL the same symptoms I felt when I was pregnant. along with some spotting for about a week now. or is this normal symptoms for being on the depo shot ???