I had sex with my wife without condom as she was near to periods. I don't wish to get her pregnant.today is 10th day after our sex.but still she has not got periods. We think that there may be a possibility of pregnancy. If yes, how to avoid the pregnancy. Please advice me the safest way to prevent pregnancy.

The safest way to avoid pregnancy is to not have sex. Other than that, you should at least use some sort of protection. You say you don't want her to get pregnant but you had unprotected sex... not too smart. Maybe she is pregnant... maybe not. You'll just have to wait a few weeks and then take a test.