Okay, this really isn't a sex question but if anyone could....squelch my worry it'd be appreciated.

I've had my period for about 2 weeks. I spotted on and off for a week and then I got it full force on the 31st and it's still around. Is this something to worry about? Or, should I just chalk it up to stress and being young (20)? I couldn't be pregnant could I? I tend to worry about everything so should I not?

thanks