Sounds like to me its a viral rash. Everytime my son gets a virus (sometimes it's so mild we don't even notice he's sick...just a little fussy or something), he will get that rash. The most commom places for babies to get the viral rash is where you are describing...the stomach, back, and chest. Most ear infections are caused when the gunk for a cold or a respiratory infection gets trapped in the ear. And lots of times the viral rash is the last symptom to show up. If he acts fine, I'd give the rash a good 4 or 5 days to go away. If it doesn't, I'd ask the pediatrician again.