breast cancer

I found what I believe is a lump on the top part of my breast.  The only time that I feel it is when my arm is behind my head.  It's sore when I push on it.  It's not a round lump.  I am thinking it's nothing because I can only feel it when my arm is behind my head.  Could this be cancer and should I get it checked out?

[Londres70]

Please have this checked as soon as possible.

Keep in mind this could be a number of things besides cancer.  

[sweetcheeks704]

I have one too but mine doesn't hurt. it's also more of a mass or clump. its above my breast more on the bone n up towards my neck. I found two others that were different a yr ago n were nothing. so im alittle worried.