Cranky/fussy baby... Help!?

Ever since my daughter was born she has been super happy and hardly ever cried. Now she's 14 weeks old and for the last 5-6 days she has been so cranky and fussy, she screeches and screams and is crabby for most of the day. The only way to stop the screaming is to hold her and not put her down even for an instant and sometimes that doesn't work either and she's just inconsolable! She's eating and sleeping as normal. She has no fever. We have not switched her formula and her routine has been totally normal. I'm pretty sure she's to old for colic. What is going on with her???