Im 17 and yesterday while in the shower i found a lump about the size of a marble under my left nipple. I know it definitley wasnt there before yesterday, it just appeared over night. It feels quite hard when i touch it but it doent hurt, however my left breast does hurt a little bit without touching it. Im really panicking that i have breast cancer but im not sure if it was cancer that a lump that size would just appear over night. Also ive noticed that over the last couple of months ive been extremely tired, and even after sleeping for ten hours im still exhausted and have no energy, im not sure if that would be something to do with the lump.