question: I am 22 years old and I have a knot on my chest next to my left breast.  I have had it for well over a year but sometimes when I do certain things it hurts. At first I thought it may be a calcuim deposit but then I wasn't sure if they form there. I am lactose in tolerate so I dont drink and eat milk products as I should. Also a little over a year ago I started drinking pop again. I drink  way too much mountain dew and plan to stop drinking pop after the new year. I wasn't sure if this could have something to do with it or not.