My baby is almost 5 months and wakes up more to nurse at night, is it time to give him rice cereal?

I've always believed that babies can be breasted exclusively for at least 9 months. I don't agree when baby docs try to get you to make your baby eat at 6 months, and I watched my mom and sister raise all their babies on breast milk for the first year, but now my baby is needing to nurse more and I am now thinking he may need solids? I know all babies have different needs, does he need solids or is he just eating more often and that's fine? He is def chucky enough. 17 pounds. As long as he's thriving, is it ok to use only breast milk?