Im supposed to get my period today but i had cramps & brown blood. i had sex with my bf last wednesday. could i be pregnant. ?

Yes, do a test: A woman can get pregnant anytime she has sex. You can wait a few days to see if you have a normal period, and if not, do a pregnancy test. If it is negative, do another test in a week. If you do not want to be pregnant, protect yourself with reliable birth control. Sexually transmitted diseases (STD) can cause changes in menstruation. Protect yourself from STD, use condoms consistently.

Home HCG test: It is hard to say. You probably should do a home pregnancy test, which is very accurate. There are many other causes of bloody vaginal discharge which may need to be ruled out by a good history and physical exam.