What Causes Pain In Left Side Under Ribs?

At night when i lay on my right side, my left side will start to hurt under the lower side of my ribs/waist area. If i lay on my left side it will alleviate that pain. This has gone on for a year now, as i keep thinking it will eventually go away.. but it doesnt. I dont have insurance atm and cant afford to go to the doctor and pay for a bunch of tests.. i'd like to atleast try to point the doctor in the right direction before i finally go. Can you please help? Thank you