Very big, painful, hard bump in my breast. HELP.?

So I went to the clinic 2 weeks ago and they x-rayed my left breast and said they didn't find any mass and gave me painkillers. I was hoping it would go away, but now, it hurts even more than before and it feels as if the bump is getting bigger. I'm planning on going back but does anyone have any idea or has been in this situation before? It feels like a ball of hard tissue, probably the size of a golf ball, probably bigger.