I gave birth to my son 6 weeks ago, before leaving the hospital I recieved the depo shot, from my research its the most successful form of birth control. However I have been told by many people its extremely easy to get pregnant during those next 6 weeks. I know I should not have even had sex with in that time, but I did... lately I have been vomiting randomly and am worried I might be pregnant again. Does anyone know what the chances of this are?

Thanks