Is it possible to get pregnant on first day of your period if its very very light?

Probably not.: If your periods are regular, and on time, you are probably close to 2 weeks out from your ovulation. Sperm lives about 96 hour so you should be safe. If your periods are irregular, and you had bleeding that is not part of a regular cycle, you should see your dr. Abnormal time frames can indicate a tubal pregnancy and should be checked out.