Is it the stress?

I took my finals the first two weeks of December and obviously this caused me to worry and stress alot. I also had a lot of sex those weeks maybe everyday, sometimes unprotected, which also made me worry. I'm not on any birth control and my period was supposed to come a week ago and I'm having trouble figuring out why it's not here. I know stress could be a factor but the possibility that I might be pregnant is bothering me. I also have the flu.