I'm new to this forum, x

I've had pain in my left underarm, I thought it was from being in the same position bottle feeding my almost 1 year old. It radiates to my back shoulder blade  at times.
I had a check x ray for another issue a while back, and wondered if it would have showed anything serious within a normal chest X-ray about my breasts. 
 

Today I went to the gp and she said part of my breast felt thicker/denser. I've been referred for a scan but I can't stop thinking about it. I'm so worried.