Does this sound serious?!

My left side is hurting like my chest my breast and it goes down to my ribs. In my chest and breast its a sharp pain but it feels like my ribs are squeezing together and its everytime i breathe and im also really weak and kind of dizzy. I dont know if this could be because I have fibromyalgia..I wouldnt think so since this has never happened before. Does anyone know what else it could be and do you think it could be serious??