You have to keep at it
How Do You Get Rid Of Lice In Your Carpet; It Has Been Sprayed And Shampooed; Are The Lice Still In The Carpet. Whole House And Family Has Been Previously Treated, But The Lice Have Returned For A Third Time.?
Try sprinkling borax (laundry section of Walmart) on the rugs it will slice through their bodies & dry them up, same with fleas,ants and so on. We sprinkle it where we see ants and on window sills & under radiators.
Maybe it is not lice, have you got a dog/cat in your house. If so, then go to the Pet shop and ask what can be done about it.
It really takes a long time to get rid of the eggs, and the nits, it might really take several treatments, and several washings to make sure they are all gone. Perhaps you should call either your doctor about this, or an exterminator, they might be able to help you out too. Good luck to you.