Washing hair stimulates oil producing glands, if you can live with it try and gradually reduce the frequency of washing - so if you do every day reduce to every other then every 3 etc. It's revolting to start wth but it does help.
I use a product called Batiste Dry Shampoo in between washes. It's a powder in an aerosol can, that you spay on your hair and brush through, and it takes away all the greasiness and makes you hair all clean and soft...and the tropical one smells lovely too. You can buy it in Superdrug.