brown discharge in middle of cycle?

I noticed yesterday and today that I had brown discharge or blood on my underwear, but it was very light, like spotting. I have been on birth control pills for 5 or 6 months and have taken it within 2 hours every day during this pill pack. I just started my third week of the pack yesterday. I was wondering if this discharge/blood could be caused by stress, because I have been under a lot of pressure lately, or if I have ovulated while on the pill because I am showing all the signs of ovulation that I had before I started birth control. Also praying that it isn't implantation bleeding. Any help would be appreciated!