Why has my period not come yet!?

I have been waiting for my period since and my last one was from May 12th - 16th,I am not sexually active so its not Pregnancy...I had all my PMS symptoms(which is usually pimples on my face and my breasts getting bigger) but d pimples are gone and my breasts is still big!What could be wrong?I am 24 and I have always had regular period,I'm scared so Pls help.