A.C.
I'd take him in to the doc and see if he might have an ear infection... If he's acting a lot different than normal then usually there IS a reason. And my daughter NEVER ran fevers when she had ear infections, the only way we knew was because she got so cranky! (she ended up having to get tubes cause she had so many) And it would explain why its only at night because it hurts their ears to lay down... (and it makes them feel better to suck so that might be why he wants to nurse)
Good luck!