bottle aversion?

does anyone know what are some causes of bottle aversion? any advice on how to deal with it? my baby is 7 months old next week, and he never had an issue with bottles until now. i’m not sure what to do…i can only breastfeed him before/after work. so far he’s only taken 5oz of milk where normally at this point in the day he should have had at least 14-16oz.