I've been were you are now its horrible. I've treated my dogs with frontline and treated the whole house with insecticide....but it did not work so well since the neighbor had one dog at the time who wasn't treated with flea stuff and some family here has very sick cats with lots of fleas. So i switched over and treated the dogs with garlic, in their food twice a week, since garlic can cause anemia cats are more vulnerable for garlic so I won't know if its a good idea to feed them garlic, since i don't own any cats. I also treated around my whole house, front and backyard. Most likely your cats or feral cats are the problem, so I would switch flea stuff and treat the whole back and front yard too. What I used was Exil Flea Free, I dont know if its available in the US? What also works wonders is spray what is used to kill insects etc. on birds, its also a spray you would use in the bird cages, I just used it in my house and front and back yard. I don't know what vacuumcleaner you use but we have here one were you put in a bag who collects all the dirt, In that bag i put few drops off lavender oil, fleas hate lavender and i also sprayed insecticide inside it. I wiped the floor (non carpet) with a bucket with eucalyptus oil once a day it even smells fresh.
I washed the dogs with a shampoo containing aloe vera, and later on I made a ''pet parfum'' with a bottle containing a few drops of aloe vera oil, and sprayed it on their coats, which is safe to spray on cats,rabbits and any other animals