I have gone through your query and understood your concern. Since a trans-vaginal ultrasound
has ruled out any abnormality, ovaries as the source of the pain can be ruled out. Spotting can occur with urinary tract
infection; vaginal spotting also can be seen due to the associated hormone disturbance. As you have ruled out vaginal discharge
through the tampon, the most likely source of the spotting is the urethra
. In the current scenario, I would ask you to see a urologist
and make sure where the spotting is issuing from, since you have already seen a gynecologist. Urine culture tests also should be done. Urethroscopy may also be needed to identify a possible source of bleeding to plan further management. Hope you find this information useful. Wish you good health.