"RED BUMPS"

Hi. My name is Nancy Lea. I am new to this forum which I joined out of frustration in not being able to find out what is causing the rash of "red bumps" on my mini-schnauzer and how to treat it. These bumps occur in varying sizes all over my dog. They start as red raised bumps and then flatten and crust over. I have been to the vet which is getting very expensive, although I have pet insurance. I have given the dog antibiotics and eliminated what food, if any, I thought might have been the cause. Has schnauzer owner out there experienced this. If so what is it? How do I treat it, before I end up in the poorhouse?