Witching hour!

Charlotte
My little girl was 7 weeks on Friday and has been up until now no bother at night. She would usually settle into a deep sleep after a bath and bottle, we would usually get 4 hours until she woke for another feed. 
Now she just won't fall asleep even though she is clearly tired. She cries like she is in pain 😞
The only way I can get her to stop crying is putting her on the boob. 
We've had 3 consecutive nights of this now. 
I breast feed through the day and usually only give the one bottle before bed.
Any advice would be great....