Girlfriend and i had protected sex for first time 2 weeks ago, now she's 2 days late for her period. should we be worried?

Not yet: Fertile couples who have sex must always be ready to be married, settled down, and with stable jobs that provide medical insurance, in case of a cute little surprise baby. That being said, the chances of getting pregnant while using a reliable form of birth control (protected sex) is very low. If worried, a home pregnancy test gives an accurate result 3 weeks after sex.

Maybe: If by "protected sex" you mean a condom only was used then yes, you should be concerned about an unintended pregnancy as condoms fail at a rate of 20% when used alone for contraception. If your girlfriend used a second contraceptive method, then it is likely that her period is simply "late" and delayed.