spotting for a week..2 weeks later spotting AGAIN

Idk what is going on but I need help. I was spotting instead of my period 2 weeks ago. exactly a week from today SAME THING except more pink/brown. I'm not on any contraceptives, no medication, not stressing, negative pregnancy test, no cramping, slight fatigue and that's it. IM NOT SURE WHATS GOING ON IN THAT UTERUS OF MINE...HELP!?