Pits are not stubborn, they are just persistent and determined. Bullheaded is another word! They may be just persistent in their own world.
Whether you know it or not, it is possible that you are givign him mixed signals of some sort, and he is actually confused. When a dog is “confused”, they tend to shut down until something else grabs their attention.
Your pup is still really young, so housebreaking hasn’t been completely established yet. It will take time and patience! Just don’t give up. When he pees, praise him lavishly and treat immediately after he does it. He will then get the idea, that hmm…I get a party when I pee. Some dogs do not poop and pee at the same time. My dog will pee first, and then an hour later, she needs to go out and poop. Why? Who knows. I guess she likes to save it for awhile longer. But you need to get a system figured out that will get him to poop. If that means you have to keep taking him out every 3 minutes, then by all means DO IT! He will get the picture soon, don’t worry! It is up to YOU and how you train your dog to do what you want it to do. Dogs aren’t born knowing what WE want; only what THEY want. It is up to us as their keepers to teach them the rules of the road.
When he pees and then wanders around for awhile, bring him back inside. Tether him to you (leash through the belt loops, etc) and have him with you at all times. When you get the signals that he has to potty again, rush him back outside (don’t forget the treats!). Eventually, he will poop, and when he does…throw him one heck of a party right there on the lawn. So what if your neighbors think you have lost it. YOUR DOG DID WHAT YOU WANTED HIM TO! To this day, I STILL do that with my dog. It just reinforces that she is to potty OUTSIDE and not anywhere else. Younger dogs will tend to take to the potty party quicker than others will.
Sometimes, a quick walk or run around the area gets the pooper working. It stimulates the colon to move and mark. If that means runnign in circles, DO IT! Whatever you can do to get him to poop is what is important. It doesn’t matter that he does it on command or not. That isn’t a big deal. It is that he does in the right spot and not in the house.
That is great that he has learned other tricks, but pottying in the proper spot is a bit more important.