I have been on the pill for 4 months and I have never had spotting or discharge of any kind. I bleed heavy on my placebo days but as soon as the week is over I stop bleeding.  But it’s currently a week before my placebo week and I had brown spotting that lasted about 2 hours and hasn’t resumed again. 

Could this be implantation bleeding ? I have sex about two times a week.  25% of the time we use a condom with the pill. 100% of the time we use the pull out method.  I take my pill everyday with the occasional 24 missed pill, I take it between 3-8 pm   

What are the chances of me being pregnant?