I Have Been Having Pain Under My Right Arm Pit,

I have been having pain under my right arm pit, around my breast also,I am getting blood test done on Monday, my Dr told me to take ibuprofen prescribed muscle relaxers, they gel immensely, I don't feel any pain..I have diabetes and high cholesterol, I was supposed to have the blood test done in November but I kept forgetting to fast. I have been reading on this subject and I am really scared...