When his poopy is hard little balls, he's a lil dehydrated. Ask ur pediatrician if u can add a lil water or juice 2 his diet, and use iron fortified oatmeal instead of rice cereal, as rice cereal can be very constipating. As long as it corrects in a day or two it's nothing to worry about. As 4 the vomiting, dehydration in a 6 month old is a major concern. Depending on how many times a day & how much. If he's vomiting everything he eats, it time 4 a pediatrician appointment. If teething is suspected it won't be that much, & it's more a lack of appetite. When they're teething they can swallow a lot of saliva due to increased production & this can be the cause 4 loose stool & /or very mild vomiting. But always have vomiting lasting more than 24hrs or more than twice in a day checked out by a doctor. Ppl will tell u teething can't cause all these problems, but as a mom I can tell u teething can cause , predispose or aggravate underlying symptoms. I've seen in my son watery red painful eyes, ear pain, lack of appetite, loose stool, and many many sleepless screaming nights. At night there's nothin 2 really distract them from what they r feeling & during the day they can be cranky, whining & difficult, or perfectly fine until