2007 Ford Ranger catalyst converter

I purchased the truck brand new and has been running fine until one morning about a week ago. I started the truck and began driving to the corner store about 1/4 mile away. As I approached the end of the block, I noticed the engine idled roughly and then struggled when I accelerated. I also notice some discolored exhaust when I accelerated. I think its the catalyst converter but I cant figure out the underlying cause. This problem began quite suddenly. I have been making very short trips regularly for the past 7 months. By short trip I mean start the truck, drive 5 mins, turn off the truck for 8 hrs, start the truck, drive 5 mins, truck sits for about 10-12 hrs. This process repeats five days a week. Can you please help the mechanically clueless?