Your're right, dry mouth is a cause, and so is a compromised immune system, and can develop drug resistnce. There are many home remedies that may be of help, if you seach, but right now you need to take the fluconozole, aka diflucan, if prescribed until completion of the prescription even if the signs and symptoms cease. Sugar, yeast, alcohol feed thrush, so you may want to limit that, and improving your immune system will help. Brushing your teeth, tongue, rinsing will also help. Thrush is easily treatable, but if not done, can go to the throat, esphogus, stomach, and possibly systemically if it gets in the blood systm which can happen through the gums, ulcer, stomach whereby it is then invasive or disseminated candiasis, which can be deadly.

Good luck.