What happened to my angel baby??

My sweet Hadleigh is 7 weeks old as of last Friday and for about the last week things have been crazy. She used to never cry unless hungry, slept perfectly fine (even with big sister [2] running around screaming), and breastfed pretty great too. Now she is super fussy no matter where you put her or even if you hold her. She has almost always been put to sleep by nursing and then cuddles for a little while but afterwards you could put her down and she would sleep great until time for her next feeding. Now when you put down you have about 5 mins to pee and check on big sister and she is up screaming bloody murder. Her nursing has also been really messed up lately too. She wants to eat every hour but only for like 5 mins and then she acts like she's full. She still sleeps all the way through the night 10:30-4:30 but I really think it's only because she is exhausting herself during the day by not sleeping unless she is right on top of me. What is happening? Am I doing something wrong? I'm not complaining about having to take care of her at all I just don't know why this huge change happened out of the blue. Any advice or encouraging words?