hi, i m 20 years old and i d just realized that i have a lump in my left breast somewhere at the lower left end of the breast, it s quite hard and big almost the same size as a grape, it s not visible though, and i feel a slight pain when i gently press it down, and for once in while, there s this pulsating pain from the area with the lump moving down my lower ribs. What might be the cause of this?