Why would the first few pancakes come out perfect, but only get worse from there?
Ah, the worsening pancake debacle. I know it well. We have all been there, even after training for countless hours to make the perfect soufflé at the Culinary Institute.

The pan is getting too hot. 

You should cool the pan with a quick rinse. This will also have the effect of resetting the surface, to get rid of any built-up grime or grease.

Good luck and happy cooking!