You'll probably be able to see fleas if you're getting bitten - when we had fleas, I'd see them on my legs sometimes.
does your house have carpets? fleas love carpets, and will have loads of eggs in there. if someone had a pet in there before you, the fleas could still be there because the eggs last for agggeessss and then 'wake up' when they sense vibrations (like you moving in). they'll live anywhere - floorboards, beds, sofas... anywhere.
we got a flea bomb, and some powder which we put everywhere. the best thing though was we borrowed the neighbour's cat who gave us fleas, and while treating her let her in the house - fleas jump on cat, fleas die. worked a treat.