3 month old not eating much...

My son is 12 weeks old, technically 3 months on the 20th..and for the last week his eating habits have been off. He use to eat 4 oz every 3 hours.. and now is eating 1 -2 oz like every 4 (or more) hours. He is still sleeping normal, maybe a little more, and is not fussy. When 4 hours have passed, I will try to feed him, but he won't eat.. just pushes the bottle out of his mouth.

His bm have gone from every other day to like every 3rd or 4th day.. I'm worried sick. I will be calling his doc and want to get a weight check.. anyone else dealt with this?