Late period but not pregnant :(

Has this ever happened to anyone before? I do tend to stress sometimes but this is what happened. My period was due on the 18th of this month and sometimes usually my period comes a day early, on the actual day or a day later than expected. But I didnt get it early , on that day or a day later and also on the 19th I got my first Gardasil shot. Does anyone know if that can delay your period as well? Please help!!!!