Any idea what this could be?

My dog has always had skin issues due to allergies but never this bad. She’s been extremely itchy for the past week or 2 and has slowly been losing hair on her stomach, legs and face and tonight I noticed her skin is very red and looks extremely irritated. She also has developed an oder. She’s on apoquel and has been for the last year or so, prescribed by the vet to help with the itchiness caused by her allergies. She’s also on a daily antihistamine. We’ve tried everything from oatmeal baths, coconut oil, aloe spray, cleansing wipes and baths with medicated shampoo we got from the vet last year, again to help with her allergies. But nothing is helping and it’s getting worse. The soonest the vet can see her is the 19th and I’m trying to avoid the animal hospital due to the cost but will go if absolutely necessary. Does anyone have any suggestions I have no mentioned? Or any idea what this could be?