What Causes Pain Below The Left Breast, And Pins & Needles On Spine & Sternum?

I have had pain in my left side, starting just below my left breast and travelling down to the last rib for the last 3 weeks. two weeks ago I noticed a nodule directly under my breast, which appeared to sit on my rib, I have since then noticed, long string like lumps appearing vertically down my ribs on the left side only, there are around 5 of them all along side each other, so if you can imagine a rib cage but with lines going the other way aswell. They are hard to push, like tendons but are very painful, they hurt when I move or breath in deeply, I have had pins and needles in the left side of my spine and constant pressure on my sternum for the last two weeks. I have had no previous surgeries, injuries or traumas, or done anything that I can think of that would have caused injury. My GP seems to think it could be a muscle tear but I think this is highly unlikely due to the fact that it is getting worse and not better.