8 week old taking her sweet time eating, what's the deal?

She was eating 5 ozs anywhere from 3-4 hours give or take. She would eat it all in about 30-40 mins. I don't time her eating, I just feed her in demand. Well for about the last 3 days she started not finishing her bottles, so instead of wasting the formula started just making 4 ozs. Then she wasn't finishing that, and she was just sucking, not eating. She takes a paci. I mean the first time I thought something was stuck in the hole......nope she just wasn't eating it. On top of all that she started sleeping through the night in the last 2 nights. Is she just going through a hunger stike?? I just tried to feed her, and she wouldn't eat, but now she is crying because she is hungry. What's the deal? No fever, no congested, and diapers are normal.