You have missed your periods from December, almost 4 mths. You are sexually active with your boy friend. You don't have any symptoms of pregnancy
. You have odorless brown vaginal discharge
you have mild cramps. Even though you don't have the symptoms of pregnancy, better to have your urine tested for pregnancy and USG to see the growth of fetus. The brown color discharge may be due to reasons like coital injury
or inflammation of cervix
and surrounding area.
consult a gynecologist - to find out the causes of missing periods and brown discharge, and treat accordingly