How Can Vaginal Itching Be Treated?

hello sir,
I am 29yrs old.from 2yrs i am suffering from vaginal itching.
consulted gyneac but the medicines give me temporary relief, no improvement. after every two or three months it occurs and stays for more than a month. i had underwent abortion for 2 times (2006 and 2008) and ectopic pregnancy (right side tube has been removed) suffering badly from itching. please help