My dog makes me so angry

I adopted my Belgian Malinois about 3 years ago and he had no problems pooping. Now, I could let him out for 3 hours and he would not poop. I have a camera setup in the back to watch him so I could pick up the poop right away. But I get frustrated having to watch him for hours to do his business. So I would go out and yell at him to go poop, and right away he would poop. But I hate that I have to act angry so he would poop. But I could leave him out for 1, 2, 3 hours and he would not do it.. Until I yell at him. Works every time, like a charm. But it turns me into this angry person. But if I don't, he would poop inside the house, steps all over it.

Anyone has any suggestions?

I've tried rewarding him with treats after pooping and it doesn't work. He only poops after I yell at him