My concern is that he might have a hip or spinal arthritis making him less able to feel an urge to go or to be able to move the bowels.
I would not try any laxatives over the counter but you can see if some fiber will help him. One teaspoon per 25 pounds of dog should do it. So a 50 pound dog would get two teaspoons of metamucil once a day.
Or you could try adding canned pumpkin, cooked winter squash, sweet potato, or oatmeal to his meals.
If the fiber doesn't help you may need to see your vet to make sure there is not an obstruction going on or to see if he needs pain meds to help him get in the right position to go.
Hope this helps you!
Please press Accept if you find my answer helpful. Want more info? Just reply on your question!
Bonuses for good work are always appreciated!
Thanks for the opportunity to help you!