Hi. I Recently Got Diagnosed With Hashimotos Thyroiditis. I Had

Hi. I recently got diagnosed with Hashimotos thyroiditis. I had a 30 day have period that ended just to few days later get another lighter bleeding. I had a pelvic and vaginal ultrasound done that showed a 19 mm uterine lining thickness. How serious can this be? My pop smear came back normal.