My aussie pup is 3 mo old he itches all the time no fleas he has done this ever since I got
Him what can I do

Please take him to your vet. He probably is allergic to something. Imagine yourself in the same boat. Wouldn't you go to a doctor for help? Poor pup! He must be miserable!

Add some omega 3 and omega 6 to the dog food or feed the capsules directly.

Itching and flaky skin can be caused by a lot of different things.

Some common ones are:
Allergies
Infection
Dandruff
Mites
Habit

The first thing I do when I notice a dog scratching is check for fleas. If you are positive the dog doesn't have fleas then I move onto natural shampoos.
Shampoo that contains oatmeal can soothe and moisturize the skin while it cleans. I always try natural methods first to avoid using chemicals or medications that may not be suited to the problem the dogs has, whereas natural can't hurt.
Coal Tar is another good shampoo as it soothes the itching.

I also add essential oils to the diet. Fish oil capsules or just some tins of sardines in oil are good ways to introduce healthy oils to promote healthy skin.

If that fails then move onto an actual medicated shampoo. I use Triocil, it treats fungal and bacterial infections on the skin.

And finally, time for the vet.
Allergies are harder to treat and you want to find out exactly what the trigger is, not just cover up the symptoms with antihistamines.
Your vet can run bloods and determine exactly what the dog is allergic to.