Since 4 days ive been getting brown discharge & it looks like blood to me & it started on the last day of my fertile window. period isnt due till 15?

Bleeding midcycle: On some occasions, ovarian stimulation from your pituitary may make two eggs mature simultaneously, which means twice the levels of estrogen. Just prior to ovulation, the drop to near zero of this higher estrogen may cause light bleeding, just like bleeding occurs at the time of your period after estrogen falls to near zero.