Buy a tube of LANACANE cream from the chemist,it stops the itching pretty quickly.You must still apply the cream your doctor has prescribed though as lanacane is not designed to clear up the infection.Also try going without a bra for as much time during the day as you can,keep the area as cool and dry as possible as fungal infection thrive in hot,damp conditions.My mum has the same problem as you have quite regularly but she is obese and sweats a lot under her breasts.