According to Healthline, spotting and back pain within a week following a menstrual period can indicate uterine polyps. Uterine polyps are harmless, benign growths that develop inside of the uterus and are linked to hormonal fluctuations. Birth control pills and certain infections can also cause spotting and pain.
Mayo Clinic explains that back pain and spotting is also a common symptom of mittelschmerz, a condition in which women experience significant pain during ovulation. The pains appear suddenly and are often accompanied by light spotting. If the pain or spotting is accompanied by a high fever or nausea, it is important to contact a health professional immediately, as these symptoms can also indicate an appendicitis.