My son was TERRIBLE at around 3-5 months old. Crying all day, ever day. I went crazy when I was told "you just have to wait it out." or "Trust me, it'll get better" I hated waiting because it sucked so bad RIGHT NOW. But I hate to say, they were right. The constant crying finally ended. He's a year old now and has off days and on days, but never anything like back then.
I'm so so sorry you're having to go thru it