Vaginal yeast infections are very common problems which are, fortunately, not a serious medical concern. However they can be very uncomfortable. Occasionally, some individuals do have chronic or recurring yeast infections. Unfortunately, they are much more common in people with diabetes. Although you are right that poor sugar control can make yeast infections worse, even diabetics with good sugar control are more prone to yeast infections because the diabetes has effects on the types of organisms that grow in and on the body and also has effects on the body's immune system.
The first step when dealing with yeast infections that are chronic is to make sure that you are not doing anything to disrupt the vagina's natural defenses and bacterial composition. Vigorous washing or any form of douching should be avoided. Although these are common popular remedies for yeast infections, they actually make things worse by disrupting the normal bacterial population of the vagina.
I suggest speaking with your primary care doctor
about this problem. In addition to making sure that your sugar control is absolutely as good as it can be, you may want to discuss the possibility of more chronic use of an antifungal medication like Diflucan which is sometimes needed.