The only way to diagnose this pup is to go to a vet....and if you have done that then ask him/her for a referral to a dermatologist.
I realize that you said money is an issue, but if you don't do something, this sounds like it is getting worse. I hate to think your pup is suffering.
When you go, just let the vet know your financial circumstances so that they hopefully will take it easy on you and order only what is absolutely necessary. A specialist is more likely to come up with a fast diagnosis.