brown blood is old blood, periods normally start out pink, veryfresh blood, before turning red, As for could you be pregnant the anwser is yes, I bleed and I mean bleed hard for 5 months was bed ridden, had to take medicine to stop contractions, but had a healthy 7 pound boy, its very common to spot bleed especially brown, was your flow lighter than normal, are your breasts tender, have they gotten bigger, any nausea, all early signs take a at home test, If your not pg and continue to bleed brown it could be some kind of infection, in either case you will likely need to see docotor. Good luck to you !!