Baby not taking milk?

Is anybody else having trouble getting their 6 month old to take milk? He's only had 7 oz all day and refuses the milk every time I offer.  It's now almost 10 pm! He's fed mostly formula and just the little bit of breastmilk I get from pumping. He has preferred solids over milk for about 2 weeks now. How many oz should they be having at this point? On a good day he'll have about 25 oz and that includes 2 night feedings.