I have very reg. cycle and didn't miss a cycle before. I had sex with my boyfriend on 9th of May and still no menstruation as of yet. I m bit worried..He used condom and not climaxed so don't know why i don't menstruate ..i don't see any reason for getting pregnant. what could be the reason? help is appreciated.

There will always be a slight chance of pregnancy even with a condom, and even if he didn't climax.
Your cycle may just be off this month, but it would be wise to try a pregnancy test to rule that out.