Drastic decrease in nursing in a 5-month-old? What to do?

[CrunchyChristianMama]

My 5-month-old is all of the sudden rejecting nursing.  She will only nurse for a short time on one side if it's been 3-4 hours since the last time she ate.  When I try to put her to the breast when she's cranky or appears hungry, she turns her head away from it, pushes back, and starts screaming. 

I'm worried that she's not getting enough milk! 

She's only eating 1-2 times in the night as well.  So she might only nurse 6 times in a 24 hour period.

I never had to deal with this with my ODD, she would eat anytime you offered and then some.  What should I do?!? 

[CrunchyChristianMama]

Of course the day I post this she goes back to normal.  She's been chowing down all day long.