Pregnant?? No Idea Wats Goiin On!

Well i went to the ob/gyn bout 1 1/2 weeks ago...he said that i had bacterial vaginitis..and i was on pills for 7 days {metronidozol} i think , well i took them all the last dose was friday july 19th and on monday i started back smoking and the next morning when i got up i had some brown discharge and i seen a little bit of blood and now it's thursday and i don't see no brown discharge it's just blood now....it's not alot but it's blood..oh yeA i know u wonderin why am i posting it in the pregnancy forum is because i looked up brown discharge and it could be a sign of pregnancy and i had sex last wenesday...when i seen the discharge i thought it was my period because it's time for my period to come on...but then when i seen that it was brown i was worried because it doen't get brown until after my period is almost over, i have no abdominal pains no lower back pain or pelvic pains...can u guys help me please! asap!