I had unprotected sex 3 wks ago and ive taken test and they are all neg.. im on bc and 4 days before my period having brown discharge am i preg?

Not likely: Not likely pregnant if you have been taking birth control as directed (assuming pills) and have negative pregnancy test three weeks later, although there is a small percentage who will get pregnant on birth control. Irregular bleeding is a very common complaint in about 1/3 of women. If your period doesn't start when expected, take another test to confirm not pregnant.