If you decide to continue using shampoo, try using a baby shampoo and add to it about 20 drops of Teatree Oil (pure, 100%, not the supermarket rubbish - there is a good reason why it is cheaper) with a tsp of olive or coconut oil (these additions are for the complete bottle, not per application). Even then, reduce how often you use it.

btw - I use the same concoction for washing myself all over as I get a rash if I use soap.