IF it keeps coming back then its in your environment.

Did you wash EVERYTHING (sheets, towels, clothing, kitchen towels, etc) in hot, hot water?

Did you leave your mattress out in the sun 2 days in a row, flipping every 2-3 hours to let the UV kill the mites?

Did you use the carpet stuff correctly on ALL of your carpeting?

Did you forbid use of the upholstered furniture even by the family dog for 3 days?

Did everyone in your family (household) seek the treatment together, even if they are not presenting symptoms?

Yes the doctor gives you an insecticide, because you are being attacked by microscopic insects.

However you have to make certain you kill all the mites in your environment.

This also includes personal hygiene tools like combs and brushes.

These things have to be washed at a temperature of at least 120F.

Further, you need to tell everyone you have slept with that you have scabies and that they need to see a doctor at the first sign of the condition.

Further, you need to refrain from sex for about a week while you are under treatment and after (allowing the eggs to die) This will help in preventing you swapping scabies with your sex partner.

Your bed, bedding and pillows either need to be replaced, washed in hot water or allows to sun on all/both sides for at least 24 hours - meaning two days of full bright sunlight so the UV can kill the eggs/larva and adult scabies mite that is in there. It will also kill most of the other bugs that naturally occur in your bedding.

If all or some of this is news to you, then your doctor didn't do his/her job and tell you everything you need to do.