6 month old won't eat and is very clingy

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My 5.5 month old has been refusing to eat during the day. She barely gets through an ounce during a feed and will cry at the sight of her bottle. She has also been very clingy lately. I have tried to give her more time between feedings. She cries because she's hungry but then only has an ounce of milk before she refuses the bottle again. She's also been very fussy and clingy. Has anyone else experienced this? What could it be?