We recently bought and moved into a house that was infested with fleas. We have a dog which we treat with frontline. We have been vacuuming the house every day for 3 months now. In addition we have had a exterminator out to spray twice. I have also sprayed (peremthryn and precor) myself a couple times in the 3 month span. The problem has definitely gotten better and we thought we had finally rid the house of the issue. That was until we found a flea on our dog yesterday. This was the first one we have seen in 3 weeks. I gave him a capstar and washed all his bedding. Should I be concerned that we are still infested?