My son was born at 36 weeks 2 days. He's 11 days old now. He's started getting really bad gas which has led to diarrhea. We give him breast milk during the day (via bottle since he doesn't want to latch at the boob) and similac advanced at night. I know newborn poop is usually pretty runny and his poop is the "yellow and seedy" that it should be but now he has such a terrible diaper rash that he cries when you wipe him. We've been putting A+D cream on him, but it's not helping and the diaper rash is getting worse. Is this a normal thing or should I be concerned.