I can understand your worry. As new moms, we always worry whether or not baby is eating enough. Is he gaining weight? Does he feed in the night? I think 3.5 hrs is fine. He will eventually be able to stay awake longer, so enjoy the sleep while it lasts
. A baby won't starve himself (barring no medical conditions), so I'd trust that he's eating what he needs. Have you expressed your concerns with his doctor? What does your typical day look like?