I am 4 days late on my period as of 2 days ago i had light brown discharge and still have it with cramps in my lower adominal area. i have the birth control in my arm but i've had unprotected sex. could i still be pregnant?

Unlikely, but...: A urine pregnancy test, done correctly, gives a reliable result 3 weeks after sex (3 weeks after when conception might have occurred), or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon, and thus lead to a repeat test. If a woman gets her normal regular period, then she is not pregnant.