Could he be suffering from reflux, or something else that is causing pain? Babies with reflux may cry when placed on a flat surface. Could you try raising his bed so that his head is up a bit, JIC this is the problem?

Try rolling him onto his side, away from you, and patting him on the bum or shoulder and see if this settles him - may take some time though. This would settle my DS who suffered from reflux around the same age.

:hugs: to you.