Your story sounds so much like mine. I've been sick with dysautonomia since 15. I'm now 28, and like you, living on a very limited SSI income. I've had good years and bad years, good days and bad days.
I take these daily: Florinef, Lyrica, Norpace, Provigil, Prozac, and Ritalin.
I take these as needed: Zofran, Valium, Celebrex, and supplemental oxygen.
I also have a central line for daily intravenous fluids. By the way, this is my 7th month without fainting.