I've been in a "friends with benefit" relationship with this guy, that i absolutely love so much for about 3 weeks., and he prefers unprotected sex

he's never "done it" inside supposedly, but I know even precum can get you pregant
my last period was about 2 weeks ago, and now I see some dark brownish things on my underwear, and cramps too..
also right now, i'm doing a lot of exams and under a lot of stress, on top of that I am catching a cold, runny nose.. and a headache
I dont know if I am just stressed out or i'm actualy pregnant!!!
any advice or opinion would help!
THANKS