Low lying placenta is a cause of worry if it persists till term ie 37weeks.
90% of the low lying placenta move to the upper segment by term by a phenomena known as placental migration.
All you have to do is follow its position with regular ultrasound
The precautions you have to take are:
Avoid heavy work, exercise
Abstinence ( avoid sexual intercourse)
Keep a record of your baby movements
Avoid staying at home alone be it while sleepin, avoid locking your room and toilet as you never know when you would need help.
Keep a check on you vaginal bleeding , incase its heavy, go to the hospital at the earliest.
For now as your placenta was low , some amount of placental tissue must have sheared off and so you are having bleeding which would go off with time. Incase the bleeding gets heavy or fresh bleeding occurs which soaks all your clothes and bedding, do rush to the doctor immediately.