Left, colicy, upper-abdominal pain radiating into your back. Nausea & lightheadedness, heartburn & headaches. Problems with your stool...
My thing is kidney-stones (and most/all things renal related), and that's got all the symptoms of a stone, or a kidney-infection (or possibly a UTI).
Colicy pain that radiates into your back is sometimes an indication of renal issues.
I'm not a doctor, and don't have enough information to tell you whether or not it's life-threatening, so I'm not much help to you in that regard.
If the pain is bad enough, you should go to the ER. They have to treat you, and at least stabilize you (and assess your current medical situation), and it's free to you, so maybe consider going to the hospital ER if it's too bad?
My 2 cents... sorry I can't be of more help. Being without health-insurance is a tough situation, and I feel your pain (figuratively & literally).
Good luck to you Sister.