The service you are referring to is something I provide. I am called a claims assistance professional.
Claims assistance professionals can audit your bills. But it isnt cheap and there is no guarantee a recovery can be made.
Unfortunately for you, without health insurance you are at the mercy of what a physician charges. However you can find out what codes he would have used if he were billing to an insurance company and ask them if they would accept the same payment that the insurance company would have made. Sometimes this could be a huge decrease in the bill.
With the hospital charges, yes you may have been overbilled. They may have charged for procedures or items that should have been inclusive.
If you care to leave your contact info, I will help.