AFAIK, This is a common issue with most puppies. Try to distract him with a toy or treat when you see him doing it. Clean up his poop immediately so he doesn't have the chance to eat it again. But yes, please seek a doctors advice.
Hi. This is a vice which mainly happens due to nutritional deficiency. Make sure you provide adequate food to your pet and include Petup pro and any Calcium syrups as well.