My son is two months old and i exclusively breastfeed. i cant meet his demands. how can i produce more milk?

While working i pump three times. my pumping for the day is the next days feedings.. i have been getting one 5oz and two 3oz pumpings. he is eating about 4-5 oz a feeding. I am having a very hard time keeping up. what can i do? any comments are greatly appreciated! help!!!!