My 1 month old hasent ben eating well...?

last night he slept 5 hours without eating then today he did this also then the last few bottles he only ate 2 oz when he normally eats 4oz every 3 hours he cryss like crazy after a feed but wnt take the bottle anymore I ran out of my last can of simmalac senetive for fussness nd gass ne he is goin bak on enfamile genttle ease for fussyness nd gass also he did fine with the gentle ease before but after having the simmalac he seems to not want to eat much I can't aford the simalac becuz wic only gives enfameal ware I live