I had it with both of the boys. I really does correct itself with most pregnancies. Because I had previous surgery for endometriosis, the scarring prevented mine from correcting. Both boys were c-section.
It is very difficult not to worry, but know that only the first one resulted in a little bleeding and a quick trip to the hospital. Now he is 14 years old and over 6' tall. The other was early as well, but only because he was 9 1/2 lbs and for some reason didn't want to wait to come out.
Partial previa should move for you--but if it doesn't, know that either way, you wind up with the same result--a beautiful baby in your arms.