No one here can tell you if the pain is related to breast cancer. Of the women I know with breast cancer (and that is quite a few now!), most have had no pain from the cancer, but some have had excruciating pain. It is not a simple "yes/no" question. The best place to start, if you ask me, is with your regular doctor. I know you don't have insurance, but a family doctor appointment is not that expensive, and he may be able to tell you what is going on. If you have still concerns, I would suggest you call your local Susan G. Komen affiliate and ask about free mammograms for uninsured women. Most larger cities have their own affiliate. You can also go to ABC News website and search on mammograms. They give a list of places to turn to if you have no insurance. The next catch would be... most places want you to be over 40. You didn't give your age, but I would call to check, anyway.
Hope this helps.
"There's a difference between a philosophy and a bumper sticker." --Charles Schulz