Its your hormones, I have the same thing, I am over 40, no cycle, but knows when It should be that time. I have no female issues. But it started about 2yrs ago.
Ps. I have all of my female organs
Since you state that it happens before your period, the cause of the itching could be hormonal. If it is more serious, which is normally accompanied by discharge is some form of vaginitis. If it is hormonal, then it will probably stop on it own. If it is a yeast infection, which is normally accompanied by white cottage cheese looking discharge, you could buy some Monistat for it. If it is due to some other type of infection, then you need to go see a doctor. They will do a pap smear and take a culture and check to ensure that you have no infections. Infections can come from unsafe sex, douching, use of tampons, wearing tight clothing or pantyhose.
My advice is to go to a gynecologist and request a pap smear. This doctor will be able to answer your concerns in more detail.
Good luck.