Placenta previa (low lying placenta)


I had my anatomy ultrasound today (18+6) and everything went well, baby girl looked great and was very active. About 10 minutes after I left the clinic I got a phone call from medical assistant at the clinic saying "Your placenta is low lying, the doctor says don't have sex until you come back and see her". So now I'm just sitting here worried as ever because I don't know how low it is (covering the cervix? Totally? Partially?) And I'm afraid of a c-section or even worse the placenta ruptures and I hemorrhage. I'm going to call my doctor in the morning when the office is open and get some clarity. I know the placenta moves up on most pregnancies but I'm just so worried.