Everything is normal, just placenta is low lying for that you have to be very careful like avoid heavy weight lifting, intercourse, long hrs of work/stress. As pregnancy progresses, uterus size increases to accommodate the growing baby which may cause shift of placenta away from internal os ( cervix opening). Follow up to be done with USG @ 20 weeks (level 2 scan) and @26-28 weeks to check placenta position.
Next Steps
Follow up with USG @26-28 weeks.
Health Tips
avoid heavy weight lifting, intercourse, long hrs of work/stress.