Jan, It wasn't clear whether this time (5 1/2 mo) was the first time
you've seen this baby, or whether you know him yourself from before. In
other words, is it the mother's report that he's always been like this or
*your* actual previous observation of this baby on the breast? If a 5 1/2
mo old crawled into my office and breastfed like you described, I'd
probably tell mom to look for teething. In my experience, kids can also
lose weight, suffer diarrhea, be fretful, otherwise goofy when teething.
Of course, as others have suggested, his behavior also suggests
allergies. Good luck. Judy K.