Since yesterday my 1 month son has been crying like crazy. I can't put him down, it took me till 2am…

Since yesterday my 1 month son has been crying like crazy. I can't put him down, it took me till 2am to finally put him asleep. I don't know what's wrong. I feed him on time and I'm changing his diapers but he's still very fussy. I don't know what to do. I'm so frustrated and tired...