Sounds like it could be an ovarian cyst or possibly something wrong with your ribs on that side. I had a huge ovarian cyst 3 years ago, and I had the same kind of pain in the same place. It hurt so bad. It was actually a tumor rather than a cyst.
Then a few months ago, I got similar pain but not as severe. I thought it might be an ovarian cyst again, or a UTI. The Urine culture came out negative, so the walk-in clinic referred me to a kidney specialist and I had a CT scan where they found no kidney stones or ovarian cysts, or nothing out of the ordinary. I finally went to my GP (I had been to a walk-in for the urine culture, and then to the kidney specialist, but not my GP), and told him my symptoms and where it hurt (from the middle of my back, around my side, and down near my ovary. I told him that it hurt worse depending on how I sit, and always hurt when I was driving and had my hand on the steering wheel. So he was like, "Oh." and poked me in the side of my back, and I almost went through the roof in pain. He said one of my floating ribs was inflamed. He had me take Celebrex (anti-inflammatory) for 3 weeks. It helped a lot. I still have pain (it's been 5 months), but it's not nearly as bad as it was before, and it's mostly just intermittent now.
I think mine was caused by a fall down my front steps back in January, and then it didn't start hurting until March.
But anyway, it sucks that you can't afford a doctor. Good luck...