baby's not happy lately :/

el
For the past three days my baby girl is not happy. She always used to be happy all the time and very laid back and super content. 
Now she's crying all the time, she doesn't smile and laugh as much, and she always whining. And the biggest thing is she refuses my breasts. Totally didn't want to hear about it. She's breastfed and bottlefed and now she only takes the bottle. 
Anyone in the same boat? She's just turned 5 months.