Exercise and Placenta Previa?

I am about 14wks pregnant and was into the doc yesterday after experiencing severe cramping, but no bleeding.  After ruling out infection, i received an ultrasound and have been diagnosed with complete placenta previa.  I will be getting ultrasounds every 2 weeks to see if it has moved.  Does anyone else have experience with this and if so, did your placenta move by 20 weeks?  If it hasn't, they will schedule me for c section.

Also, what exercises can I do while I am diagnosed with this?  I am on pelvic rest and she said nothing really intesne, but does that include yoga?