Barely eating and constipated?

Aud2314

I'm waiting on a call back from the pedi...but thought i'd also ask here.  DD had her shots Tuesday...was very tired and eating habits changed for the last few days..but she was still eating atleast.  Last night she ate ONE oz (she is 2mo) at 7pm...then I tried to get her to eat more after I changed her at 8 and put her jammies on and she would NOT have it...cried and screamed.  So, I put her to bed assuming she would wake up in like an hour to eat....NOT.  DD is not a good sleeper, and she seriously slept from 830-2am (longer than she ever does in one stretch)...on ONE ounce...and then barely would eat 2 oz at the time she got up! I could hear her tummy rumbling.  She fell back asleep for 3 hrs, and then again i had to fight to get her to eat barely 2 oz.  This morning she finally pooped and it was hard as clay (and big..how she got that out of her I will never understand). 

 Has anyone else experienced such a drastic change in eating even 3 days after shots?  She usually eats 3-4 oz every 3 hrs....