6 month old not eating as much?

dpraseutsinh

my 6 month old just recently started not eating as much as she used to. she used to eat every 2 hours 4-6 oz. but lately she's only been eating about 2 oz every 2 hours and sometimes she won't eat at all and will mostly just chew on the nipple of her bottle. her check up was yesterday so i asked the dr about it but he said it's nothing to be worried about. i asked if she was teething and he said he doesn't feel any teeth at the moment. 

 what else could be the reason she's not eating as much?