Ah mama, maraming of us have been through this at 12 weeks at actually yung placenta nag-migrate higher as pregnancy progressed, so it's really common and your doctor's right na hindi ka mag-aalala. The best thing is just follow up with your OB regularly at mag-enjoy ng pregnancy, stress talaga ang enemy nito, so try mo mag-relax, avoid heavy lifting, at take it easy when you can. A few of my mum friends who had the same situation delivered normally in the end, pero siguro just confirm with your doctor sa next ultrasound kung paano na ang position ng placenta mo para safe ka lang. You're gonna be okay, promise!