Help! My cat is eating her fur and losing weight...

[NiveusFox]

Hello, I'm Amber. My 5 year old kitty, Gizmo, is really starting to worry me. About a month ago we've been hit with fleas and we have four cats. She's been having the worst time, as she can't seem to stop herself from eating the fur off her back. I've combed her and she actually doesn't have very many fleas. I wonder if she may have had a bad reaction or may have been allergic to a flea medicine we tried. Anyway, it's gotten worse because she keeps eating her fur and seems to throw up her food along with it. Her weight is really worrying me. Today she once threw up foam, and I read that that indicates there was nothing in her stomach...

Please help! We've had to deal with fleas about every summer but I've never had any of my cats get this bad before. I'm hoping there's something I can do from home without needing a vet (as I'm financially seeing tough times right now), but if there is no other option I would like to know what I can expect from the visit... what may be wrong with Gizmo, what tests may need to be taken, etc.