I Just Got A New West Highland White Terrier Puppy. He Is 8 Weeks Old And Is Perfect, Besides His Pooping.?

He poops about 6 times an hour, and he seems to strain himself when he poops. He sometimes whimpers. He isn’t constipated because each time he tries, he poops. The poop isn’t very hard or very soft, it’s right about in the middle. I don’t understand what would be making this happen. He eats fine, doesn’t throw up, and is active. He just has this pooping problem.