I have a different strain of yeast, which only occurs in weakened immune systems im hiv negative so what else could be the reason?

Yeast treatment: I agree with Dr. Raff's reply. I would add that you might have misunderstood about yeasts and weakened immunity. Up to 10% of all vaginal yeast infections are caused by yeasts resistant to the most commonly used treatments like "azole" drugs (clotrimazole, fluconazole, etc). They usually have nothing to do with reduced immunity; it's just bad luck. Alternate treatments are available and effective.