I'm so sorry to hear about your pain
Let's see if we can help.
You haven't specified which medication you were prescribed, but there are yeast infection treatments that list burning as a side effect. Because you're expressing this amount of discomfort, I wonder if you're able to ask your doctor if they can talk about different medical options for you. For example, is there an oral option? Can the doctor assist you with placement if the internal option is the only one available? What types of medication should be used internally, and which ones shouldn't?
Also, on the matter of toilet paper and sensitive skin: I would ask your doctor if it's okay to use generic TP to wipe. Otherwise, you can also ask them what they recommend for people with sensitive skin. To give my own suggestion, I personally like to use baby wipes that are meant for sensitive skin (no fragrance, alcohol, parabens, or latex) and they work well for my dry, sensitive skin. If you're worried about how the material might affect you, you can try a swatch test by using the product in a slightly less sensitive area first, like the inner thigh.
Good luck to you!