Are you referring to a payment-in-full within 90 days policy? I have noticed over the past couple of years many specialists, ESPECIALLY psychiatrists, have become quite unpleasant about this. My own psychiatrist demands payment in full UP FRONT even if you have insurance, and won't even see Medicaid patients. There are signs all over the office. It's not fun or nice.
On the other hand, I keep going to him because he's awesome. Every time I go to a GP to save money something awful happens because, nice and (relatively) affordable as a GP can be, they don't have the training to dispense psych meds correctly. So I think your doc is probably right--a psychiatrist would be good for you--but how to get into one?
It's insane. The medical situation in this country, especially for people with mental illness, is cruel and unusual, and... insane.
I am sorry you are going through this. Could you ask your GP office for help with the situation? Sometimes they will mitigate. Good luck to you.