Yeast infections are notoriously difficult to treat, and I am sorry that you have been suffering with these so regularly for so long now. At this point, you need to be treated fully, and since the creams are not working for you, I would recommend speaking to your doctor
to see if a systemic (likely orally given) medication would be right for you.
That being said, however, there are some people that are prone to recurrent infections despite the best medical therapy. Pregnant women are one of these groups, but you mention that you are not pregnant. Diabetics would also be at an increased risk for almost any infection. Other factors might also play a role, but anything that compromises your immune system, such as HIV could also be a possible cause of the fact that your body can't seem to get over this.
While that is unlikely unless you have risk factors, it is clear that you do need something to help your body. Fungi are normal flora in the vagina, meaning that they usually are present. For some reason, your body doesn't seem able to balance the normal with the abnormal. Please see your OB/GYN for further therapy.