I am a 27-year-old female experiencing persistent light spotting for the past 11 days after my last normal menstrual period. The spotting is red and brown in color and is very light—I am not soaking pads or passing large clots. I do not have severe pelvic pain, fever, dizziness, or foul-smelling vaginal discharge, I occasionally experience mild nausea and back pain. My recent transabdominal pelvic ultrasound was normal, showing a normal uterus, endometrial thickness of 5.7 mm, normal ovaries, and no fibroids or ovarian cysts. My thyroid function tests done in February were also normal. I would like to know the possible cause of this prolonged period