It could be Costochronditis, you can search it to see if your symptoms match up. A lot of people with Fibro have Costo.

I was diagnosed with costochondritis by my cardiologist. It is an inflammation of the junctions where the upper ribs join the cartilage that holds them to the breastbone. I am not sure I agree but since fibro affects muscles and causes pain I feel it is all related to fibro. I have a terrible time with bras. Have treid all kinds, now use sports bras mostly. Hope that helps a little.

Thank you everyone

I have great pain all the time under my breast. I finally went to sport bras, but I am large breasted and I look terrible in them. So I wear regular bras when I go out especially to church and take it off on the way home! HA HA!

Gall bladder is under last rib on right side. Worst pain I've ever felt