Suggest Remedy For Delay In Periods

ok..im 19yrs old and recently had unprotected sex about a week ago. later that week i went to the clinic to get a depo shot. the problem is that my period hasnt came on yet! could the reason be because the shot caused my period to delay? i havent had any pregnancy symptoms but some mild cramping and some nausea..i need answers now because ive been very stressed and i dont know whats going on!