breast feeding delimma....

my baby is almost 2 months and i have been EBF'ing him.... since i will be joining work soon i express breat milk and give it to him through bottle so that he doesnt have problems settling in the new routine....

so coming to the point - i used to pump 6 oz after every 6 hrs and it fulfilled my baby needs but since last week i got less then yesterday it dropped down to 2 oz after every 6 hrs and today its just an ounce....

what shall i do to get back my supply? my baby is starving and i cant see him like that i even tried to give him formula yesterday but he refused to take it.... please help