How can I remove brown discoloration from my skin?

For the past several years, I have been dealing with brown spots on my chest, back and neck. I go to the doctor every time they reappear and I'm given a prescription to remove the discoloration. However, I'm in a situation where I currently have no medical coverage so I can't go to the doctor. Is there an inexpensive, over the counter product that I can use to get rid of the awful lookins?