Colic babies

An

Do they diagnose colic, or is it just like a “he has it because he cries for hours at a time”? I have GOT to figure out what’s wrong with my baby. He’s never happy. Cries almost all day. He cried for like 4 hours last night. This is after being fed, burped, changed, held rocked everything in the book you name it. But he is never happy and it really makes me sad because I don’t know what else to do!