That's extreme and not common for yeast infections. You sound like you also may have more going on. A rash like contact dermatitis or yes, a different fungal issue than yeast. You need to go back to your doctor about the sores that are spreading. Are you sexually active?
I understand what you're experiencing because I'm in the same situation as you. However, it seems that your condition causes more symptoms than mine. I get redness, itching, swelling, burning and discharge, and fortunately I don't experience blisters and sores. I took oral tablets, tried prescription ointment but nothing really helped. Yesterday the pharmacist gave me a topical cream called Fugacil. I'm still not sure whether it works 100% but admittedly my swelling and itching reduce so much after several applications. Just suggest it. You can see your GP and ask them for advice. Hope you get well soon.