tomw, I'm finding it hard to compose this because I don't know that much about your situation...so forgive me if I get things wrong.
It sounds like you have the skills and abilities to more than get by, yet your monthly situation is spotty.
I feel really stressed if I can't predict my income for at least the next 2 months.
I dunno...have you considered a lower income type job? The pay is less, but it provides some stability. You can always supplement it with the medical testing work. It's not forever, and you don't even need to put it on a resume. Getting out and being busy might be helpful.