well my last mens was sept. 7 me and my bf is sexually active since my period has finished. on the 30th of sept. we had unprotected sex. then on the 4th of october i have this brown spotting that last on october 5, now i still have no period and my nipples were sore and hard, and i have this lower back ache every now and then, most of the time my stomach is bloated, could this be a sign that i'm pregnant? please answer tnx :)