Help! My dogs fleas wont go away?

I took my dog to the dog park and he got fleas. We gave him a flea bath and then proceeded with flea medication and he still has them! Oh, and we treated our carpets with the leave in treatment all night last night (all treatments were today except for carpet treatment) My husband just picked off another flea! What do we do? I should mention, we give our dog flea medication regularly so I don't understand how he got them in the first place.