Q. During winter time my dog tends to have bouts of bloody diarrhea, yelping when having a bowel movement, & vomiting. Still has appetite and drinking.
A. I would take him for a check up to rule out any underlying illness. Yelping while having a bowel movement is not normal. There should not be blood in the stool. It sounds like a GI infection or illness which needs to be addressed. It could also be food sensitivities causing this but for now, this dog needs help getting the symptoms under control and treated.
I would also look into switching his food to something easier on his stomach.