Pregnancy is always possible with unprotected sex. Some days make you more fertile than others, but none the less, pregnancy is possible. If you miss your period this month, you need to take a pregnancy test. If you do not want to be pregnant at this time, you need to talk to your doctor about a reliable form of birth control such as oral contraceptives or an IUD. Continuing unprotected sex will likely lead you to pregnancy.
No you wouldn't and never would be a hundred percent safe , where possibly unless trying for a baby use protection , hope this helps
From pregnancy? No. Do you mean 4 days after your period started or ended? If you mean 4 days from when it ended, and it is not too late for Plan B, and you don't want to be pregnant, you might consider taking Plan B.