He's 12months, have you tried cow's milk?
The idea being that if he will take it, then you could start mixing half and half and then 25/75 and hopefully 100% BM eventually?
I mean, it might be a long shot... But something like that might work.
SAHM to Magnolia May (09/10), Luke Russett (04/13) and expecting 11/16. Wife and best friend to my airman.