Your doctor is right about the fashion shoes. They are useless and will often cause you damage.
Nike have a new light weight running shoe, which is apparently designed for athletes. It is only guaranteed to give support for the first 20mins.
This is a great place to try. I don't know if you have one local or not.
They will watch you run and suggest the best trainers for your style of running.
http://www.runandbecome.com/index.htm
The owner is sick in the head! He once ran a marathon and then turned around and ran back. Just for the hell of it LOL!
Predator