How often do newborns pee/poo? Diarrhea?

Today, I was airing the buttocks of my 30 day old baby to help with diaper rash (small bumps around the anus). Over the course of two hours, while he was lying on me, I noticed he had at least 6 small bowel movements (one puddle at a time). The stools were runny, yellow like mustard, but not entirely uniform in texture, some parts were more watery. He also had some problems with spilling up milk, he's been quite upset last night, grunting the entire night , which I suspect is due to the diaper rash.

Is he having diarrhea?