It's very rare for women to get pregnant the week of and directly after their periods, assuming their cycles are regular/normal. The second and third weeks are higher-risk days. If you're having your period, you're shedding the lining that makes your uterus ready for a fertilized egg, which is part of why it's less likely you'd get pregnant. You might want to check a site like www.webmd.com for more details from the experts.
Yes and no because the times that you area likely to get pregnant are when you r on your period, and two weeks after.
You ovulate before you period. The egg has to be there before the sperm. Depending on your cycle you ovulate (if you have a 28 day cycle) 14 days before your period. So yes.