For the past 4 months i've had light/dark brown spotting in place of my period with constant lower abdominal sharp pains. any idea what this could be?

Missed ovulation: You likely had a normal, common occurrence known as an anovulatory cycle (your ovary didn't release an egg this month). You should get evaluated by your ob/gyn -- they will do a pregnancy test. If this is negative, they will likely give you a short course of Progesterone to induce your period and "reset" your cycle. Depending on your exam findings, they may also recommend a pelvic ultrasound.