L.G.
Hi J., I'm a Mom of three and Grandma of almost six,a week is a little too long for diarrhea from teething. It may be some juice that you are giving him or something he is eating like too much fruit. My pediatrician always suggested that I put weakened sweet tea in my babies bottles to help curb diarrhea, if you have some iced tea just add water to it. I would also call the doctor if none of this helps, you don't want your precious one to get dehydrated. Hope this helps.
Hugs
L. Gilliam