... last period was but I know I haven't had one this month My periods have never been super regular and I had an app keeping track for me until my phone broke my Nurse told me to wait 7 days before having unprotected sex and I did but now I'm seeing on certain websites that it can't work if it's not administered unless you've taken it with in 5 days of your cycle I had unprotected sex on the 15th and still haven't started my period could it just be from the shot?