What Causes Recurring Itching Between The Thighs?

a few yrs ago, i had a very bad itching between my thighs.. i got it checked by a doc, who said it was fungal infection & gave me an lotion, after which it became ok. however, the itching started again within 6 months & is now constant for the past 3 yrs. no medicine has been able to cure this.. i don't know what to do... Please advice!!!!