Alam ko ang anxiety mo, mama, one of my mum friends had low lying placenta din at nagspotting siya around that time, and honestly nakita niya na lumaki ang baby normally sa next ultrasounds nang wala nang bleeding after the rest at meds. Brown discharge is usually a good sign kasi old blood na, so try not to worry too much lagi. Since your OB said it's normal for your situation and you're already on Heragest, just stick to bed rest talaga and follow her instructions, mas laging kasi nila makikita kung may improvement through your check-ups. Maraming cases din naman ng low lying placenta na normal lang ang pregnancy progress, kaya stay hopeful!