My period was suppose to start thursday(Febuary 24) but I got on the birth control shot monday(Febuary 21). Isn't my period still suppose to come on? So my question is could I be pregnant and if I were to be, would my baby have birth defects because i'm on the shot?

it is very common to not have a period at all while on the shot! i was on it for 3 years, and never had a period!