Get some Borax (one box does 500-1,00sq ft), sprinkle liberally on all carpeting, then work in with a stiff broom. Wait at least 20 minutes and vacuum up. Get some kind of spray to spray under couches, lay-z-boys, beds, dressers, and any other "shadow" place you couldn't get to with the borax.
That SHOULD get rid of the fleas in your house.
I have 3 cats. One we inherited when we moved in. It had been abandoned by the previous tenant, and was FULL of fleas. We gave all three a flea treatment, and did the Borax and spray. They're indoor only cats, and we've never had a flea problem since.
You can go to a pet store and get their expensive flea powder, but it's mostly Borax anyway.