I was gong to say reflux for Kat as well. My DD (also Katherine!!) has silent reflux until about 8 months. She would cry constantly and feed ALL the time. It's a catch 22 thing, they want the milk cause they have reflux (heartburn) but it makes it worse in the long run. She also didn't like lying down and would do better on her tummy. Maybe get a GP to check her out. If it is reflux, there's a lot that you can do.
Hugs honey, this sounds like a hard time for you. xx