birth control

so i'm in college and i've never been on birth control but i've been dating this guy for about 5 months and my friends really think i should go on birth control. we use condoms all the time and i've never had a pregnancy scare but i feel like i should be on it too. my friend has 6 months supply of Vienva pills (and she gave them to me just in case) because she got an IUD. would it be bad if i took the pills? does anyone know of any bad side effects?