birth control, spotting, breast tenderness, abdomenal pain/discomfort

i am 17 yearsold. i been on the ortho birthcontrol pills for 3 months. i havent missed a day whats so every.i have a normal period. but this is where the thing begins. i got my period on march 5 intill th 10 on the 11,14,17 thro 21 i had sexual in counters with my current boyfriend. starting on the 19 of march i began getting brown discharge. i assumed it was my period probably changing cycle. my period hasnt came yet and still the brown discharge continue its been 7 days w/ it. i do have breast tenderness, and wierd lower abdomenal discomfort. i do suffer normally from constapation but its gotten no better. i wanted to know is it the pills even though the spotting started on my third month? could i be pregnant? isnt it to early for symptoms if so? what could it be ? please help with advice and info thanks