I've been getting brown discharge in my underwear for the past week; it started out light and has gotten darker. I'm not due for my period for another 2.5 weeks. I am sexually active, and had sex 3 weeks ago. I don't know if this is a sign or not. I've also been getting nauseous, shaky, hot flashes, hunger. I just need to make know if I'm pregnant or not, and if I should be doing something.