She is 20 weeks old.
oh my God the shouting
I had one like that, whatever I did she grizzled about it. She had colic but also seemed to just be generally unhappy. Even though it's really frustrating there's not a lot you can do, I had mine in a sling and even though it didn't stop her grizzling I thought that it was best for her to still be held and be close to me so that she was aware of my being there.
I even took her to an osteopath to see if it could help and while she was a lot calmer afterwards (apparently her diaphragm had been squashed during birth, she was born very quickly) it didn't stop straight away.