Pregnant or paranoid?

My periods are usually right on the money. the last Friday of every month I get that lovely surprise of a bloody vagina. But this month it's late by 3 days so far and counting. My breasts are tender, I've had weird white discharge, no mood swings. My boyfriend and I had sex a few weeks ago but it seemed safe, I was just off my ovulation cycle and he pulled out way ahead of time. I have been stressed lately with school and money, but does that make a difference? What do you think?? Should I be worried?? I don't want to bring it up if I ha e nothing to worry about