pediatrician says my 9 month old shouldn't be breastfeeding

As much as he does, and that's why he's always hungry. 
My supply seems to be getting lower.  I've tried all the foods and I drink 120 ounces a day of water, and I eat almost 2000 calories a day, I'm feeling defeated and like I'm starving my son. 
I do give him solids the last four days he does seem happier, I just don't believe EBF-ing a 9 month old is bad, can't you breastfeed well over 3 or longer if you want and your body produces milk? 
I wanted to make it to at least a year and now it seems like baby will be done sooner. 

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