scabies is a human parasite so some "human" in your midst could be re-exposing you. scabies mites do not live very long in clothing but they can live a long long time under your skin. even after they are successfully treated the itch can last quite a while giving a false impression of a reinfestation or non-cure. there are many skin conditions that can mimic scabies so in order to confirm the accuracy of your diagnosis you may need to see a dermatologist and have a diagnostic skin scraping. if you still have an infestation there are other (prescription) medications that kill scabies than the one you are currently using.
we've used premetherin washed clothes and linens in hot water and still have gotten scabies 3 times in 3 months. why?