Hey, I have a small lump, about pea sized, on the back left of my neck. It does not hurt, unless I constantly press on it. Over the past year, I have also been having pains in my chest when I breathe, and am short of breath a lot. Also, my legs have been feeling really weak sometimes, to the point where I can't stand. I don't know if these are all related, but I am worried about the lump being some kind of tumor/cancer. Can anyone help me?