J.,
Your baby is so smart-- for him to choose breast milk over other food at this age is exactly what his body needs. Breast milk is the PERFECT food for him, and nutritionally complete. It changes composition as he grows, to address the nutritional needs he has at the age he is at. Isn't that just so amazing?
I've breastfed five babies, four of whom didn't start solids until they began to make clear to us that they really were ready to begin eating bigger-people foods. This meant that they were anywhere from 9 months to about 13 months old before really beginning to eat foods on a regular basis. My fourth baby got probably 95% of her nutrition from breastmilk until she was 13 months old. If you research the nutritional benefits of breastmilk, you'll find that they truly don't need anything else for a very long while-- much longer than our society and our pediatricians understand to be true. That we in our country start giving our babies foods during the first half of their first year of life is really a bad habit rather than having any sound nutritional roots. The sooner our babies first are introduced to foods other than breastmilk, for instance, the more likely they are to develop allergies to all manner of things, not just that particular food. Doctors either don't know or don't tell this as a regular course of practice....
I'm including a link to an awesome resource you've likely heard of-- La Leche League. This page is about what makes human milk so special and perfect for babies. You may already be aware of a lot of the facts on this page, but some of it isn't common knowledge, and it may calm your fears about your baby needing other foods to remain healthy.
Here's the link: http://www.llli.org/NB/NBMarApr06p82.html
None of the babies I nursed who started solids late by pediatricians' standards, or the norms around me ended up to be picky eaters or not liking foods. They all love good, healthy foods now, and are very healthy kids. In fact, the good foods that you and your husband prepare and that you eat will influence your breastfed baby's tastes in a big way: the flavors come through into your milk, and these are the foods that your baby will be drawn to. (An example of this is how mothers in some cultures eat very spicy foods, and their breastfed babies become accustomed to the spices, as it shows up in diluted amounts in their mamas' milk!!)
When my pediatricians asked me if my babies were on solids at their checkups, I just smiled and said yes, and that all was well with that. I wasn't lying-- they were eating a few solids here and there, but their main source of nutrition was exactly as nature intended: the perfect milk coming from their mama.
Good luck, Mama. You are such a good mother for being concerned about your little one, and your baby was so fortunate to be born to you!!
Warmly,
JennyC.