Can a girl get pregnancy symptoms as early as 3 - 4 days after unprotected intercourse?

no, most teenage girls, like yourself, want to be pregnant and since they want to be pregnant, it makes your mind make you think you are pregnant. You do not get pregnancy symptoms until the earliest of 3 weeks. And that is just blue veins leading to your chest. So no, you definatly can not get symptoms after 3 or 4 days.