Have you tried changing the temp that you're baking them at? It sounds like you might need a lower temp with a little more time for cooking. No expert, but sounds like the next thing to try tweaking with.
It actually sounds ike your temperature is too low.
Another thing to try is to refridgerate the cookie dough before placing it on the cold tray, then make sure your oven is preheated to the right temperature (whack it up a few deg by the sound of it) and you should be good to go.