Ma wee one was exactly like this before we came to Scotland to visit our family. There was even a point were we had to carry him about and see other people to cheer him up. What worked for us is buying a bunch of new toys and sit him up in the highchair playing with a whole bunch of new toys.
He would also be grumpy in the morning, we just gave him some cereal in his last bottle at night. That helped. The early morning grumpyness was actually hunger, the daytime grumpyness was boredom. Changing positions and me playing with him wasn't enough anymore...