What causes frequent yeast infections and what are good methods to do to prevent them?

Antibiotics, diabete: Frequent yeast infections can be caused by elevated blood sugars. You should be screened for diabetes. Also frequent use of antibiotics disrupts the body's normal mechanism for controlling yeast . Antibiotics can kill 'good bacteria' which normally keep yeast in check. Take probiotics and/or eat yogurt with active cultures especially when taking antibiotics.