Congratulations Rob!
Oral thrush, basically an out of control yeast infection, can be contributed to a number of things including antibiotics, diabetes, dentures, dry mouth, weakened immune system, and of coarse cancer treatment, all of which you may be familiar with, and basically thrives since your body can't maintain the proper balance of good/bad bacteria. Thrush feeds on sugar, yeast, alcohol, and processed foods, so limited those may help, but heard Manuka honey, as mentioned, has antibacterial properties that may help, probiotics too, if the immune system is not severely compromised, brushing, rinsing after meals, before bed. You could also have become resistant to the fluconozole, which may be switched to a different azole medication like clotrimazole or need of an increased dosage, nystatin, antibacterial rinse or other medication. I also heard of other thrush home remedies, but will let you search that out, and improving your immune system. Btw, as far as I know, peroxide dries the mouth, usually rinsed after using.
For the sake of others, and I'm no expert, but just mentioning it's very curable, if treated properly, but oral thrush can get out of control, especially with a compromised immune system like with cancer including its treatment, and can go to the esophagus, stomach, and then blood line, even through the gums or an ulcer in the mouth, and becomes invasive candiasis throughout the body, also known as disseminated candiasis, can effect the organs, and is difficult to treat, usually by a strong IV anitiviral and antibiotics, and can be deadly as high as 40%. This happened to me in 2009.
As usual, consult with your doctor. This OCF link explains it better than I can for those interested.
http://oralcancerfoundation.org/complications/candida-infection.php