I had sex on 29/3/2014,I had periods on 27/3/2014 will cause a pregnancy ?

Its certainly possible. Many women DO get pregnant on their period. You have to treat every day as a day you can get pregnant. THere really are no safe days... only days that are more or less likely.

Possible, but not very likely. Generally you won't ovulate at this point in your cycle, but you could have an off cycle on occasion. As smoothy said, there are no 100% safe days. Always use birth control to lessen the odds.