Depo and pregnancy

Patient: I had a depo appt in oct 12 2013,,i missed my appt and havent been on it every since….i had my period in feb march and april but in april my period has became brown….ive been having these weiry feelings in my stomach and im wondering if im pregnant or how soon can i become pregnant ive been off for 6 monthss now please help me

Symptoms: Fatigue bleeding cramps nauzea