How do you know if this is a problem with your child? My son doesn't shed tears, ever, when he cries, but he doesn't have dry eyes. I didn't realize this until last week when I started sitting for my neighbor's son, who is also 8.5 months, and when he cries, tears stream down his cheeks! Any thoughts? Suzanne (Mom to Glenn, 34 weeker, 8.5 months)