Did you try that new pharmacy card that they were advertising recently?
Many of the religious based charities eg Catholic Charities have a program to help with medication costs.
Have you tried calling the SW dept at the biggest local hospitals? They should have a list of programs.
Believe me I know how difficult this is. I was without my medications for many, many months. Finally someone here pointed me to needymeds.com which is how I got mine last yr. This yr I'm getting them free from a large local teaching hospital that runs a free pharmacy based on need.
This may be a long shot... but did you get the SSI info from an examiner in your local SSA office? I say that because the 800 number for SSA is hugely and notoriously wrong. The Medicaid piece of the SSI is by state not by SSA. That is, even though you don't qualify for the monthly cash from SSI due to the income, sometimes the child can get Medicaid from the SSI qualification under the state rules. Having been dealing with this SSI nonsense for awhile now I can say that the only informed people I've ever found are the local SSA examiners.