Suggest Treatment For Delayed Periods

I had unprotected sex with my GF on 19th of march and her period starts every 7th of month and now her period is blocked till today (14-04-2011)
please suggest me some tablets which is easily available to start the period. and if is it pregnancy than tell me name of anti pregnancy tablets and usage of that.
I hope u will send me the name of tablets and will help me.