Placenta previa

So I just had my 20 week ultrasound yesterday and the ultrasound tech said I would probably be sent back for another ultrasound because my placenta is covering my cervix. I didn't think much of it until today when my dr called and said she got the results of my ultrasound and that I was not able to have sex or lift anything even slightly heavy and if I have any bleeding at all to call them immediately or go directly to the ER because I could hemorrhage and die... If it doesn't move I will have to have a c section...  I'm freaking out now!!