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method ur following is safe period method, since ur cycles are regular the unprotected sex during safe period will not make u pregnant, it is the same in other women also whose cycles are regular.
But its not always safe some times there are chances of becoming pregnant, better to have unprotected sex for first 7 days of the cycle.
If everything is fine u can become pregnant if u have unprotected sex in fertile period in first month itself.
Hope I have answered ur question,