Am 23 year od and I had an protected sex for 3 months.sometimes we did an unprotected sex but he had ejected out.I didn't got my period in month of April its late by 12 days.whats the rason behind that.I am not even sure that am pregnant

There is only one way to identify pregnancy, with a pregnancy test.

ANY time you have penile insertion you risk pregnancy. Using birth control only reduces the risk, it doesn't eliminate it. And the withdrawal method is the least effective way of reducing that risk.