HELP! Suddenly he won't go to sleep!

I am not sure what is going on!
My DS is just over 4mths. Suddenly he won't settle at all in his cot or anywhere flat (including in my bed). He can be fast asleep in my arms or DH's arms and as soon as he touches the mattress, he rolls over onto his tum and screams and screams ... this goes on for HOURS!
He is very strong and I am not worried about the tummy rolling but he just won't sleep!
We keep a good routine and he is extremely tired!

Any advice? I am heartbroken ....

are you bfing? could you have a nice warm bath and a feed to relax the both of you?

Ummm, i do know DS did this at about this age, all of a sudden his senses heightened and he was basically overstimulated and had trouble drifting off....

What about some baby massage? a wind down time? i have a wonderful massage book for babies if you want it?