Some babies take longer than others to really be interested in food too. I've heard of a 10 mth old who was still exclusively bf because he just wasn't interested yet in eating other foods. And he was one of the chubbiest bubbas I've ever seen! If you keep it calm and relaxed and he has the opportunity, he'll take it when he's ready. A baby's digestive system is really only ready for food other than bm sometime between six and nine months, so perhaps your DS is just smart and delaying it because his system is only just getting there.