Yes, it is possible to get pregnant while you have your period.
Some women will ovulate more than once a month. While it is not common, it is still possible.
As for the 'prime' time to get pregnant, the idea that every woman ovulates on day 14 is not necessarily true. Not every woman has the perfect 28 day cycle. Some have shorter, some have longer.
If you are concerned about becoming pregnant, always use protection.