it is hard when you hear anything that they say is a worry (even if it is only a little worry).

To reassure you, I can tell you hat I had the same thing (I think mine was closer though) and I was told that in most cases the placenta will move up as the uterus grows and they re-check at aroun 32-34weeks. It did for me and I had a natural birth.

Like Kitten2b said, if you have any bleeding make sure you go to the hospital.