For the past couple weeks my 4 year old male cat has spent most of his
time pacing up and down the hallway, going from one room to another,
while meowing most of the time.

The only time he stops the noise is when eating or sleeping. The noise
makes it very difficult to sleep, and I doubt I sleep more than a 2 or 3
hours a night.

Last year he was treated for flea dermatitis because some of his hair
was coming out, but at the time he did not pace the floor, constantly
meowing.

He has begun to lose some hair on is back legs again, but he doesn't
seem to scratch or chew much.

Last year the vet gave him a steroid injection and some pills, plus I
put Frontline on him.

Has anyone had this experience of a pacing, meowing cat?

Also, does anyone know how the flea bite dermatitis begins? Not what
causes it, but how it begins. As I said, the cat is 4 years old and
began losing hair only last year. Why didn't he react that way to fleas
before last year?