It's best to always offer the breast before solids at this age, even up until they are 12mths of age. BM is the main food until 12mths of age (as you probably know ).

My DD has never been a huge eater so I never had to worry, she always loved her boobie milk I think as long as you keep offering it to him throughout the day then he should be getting plenty.

Hopefully someone else can give you some advice that may help.