My son had thrush that was keeping his yeast infection alive. I never did see the white splotches that are supposed to be there in his mouth but the doctor did, and once he got the medicine it helped.
Also, read your instructions on the ointment. I was gobbing it on at every diaper change and it was actually supposed to be a very thin layer only twice a day.
Also, I understand in your current situation even a small co-payment would be a stretch but you might explain your situation to your pediatrician - sometimes they have cash price discounts or are associated with a nurse practitioner that might cost less that you might be able to swing if this goes on for much longer.