Armpit Bump and Weakness: Causes, Symptoms & When to See a Doctor

Question
About three months ago, i had a small bump under my left arm.  the doctor gave me an antibiotic and it went away. Today, my right arm felt weak all morning. when i took a shower i noticed a large bump in my arm pit.  the bump itches, is very tender and my arm still feels week. I'm scared that this could be cancer.  for the past month, i have had bumps appear on my head, they too itch a lot.  then, after a day or so, they go away.  could this all be related?  I'm worried that this is some kind of cancer and it is spreading.  I went to the doctor today and she ordered an ultra sound, but I'm scared that she is missing something. Please help!  Are these any signs or symptoms of something specific?

Answer
From the description you have given I doubt very much that this has anything to do with cancer at all! I think this most probably is an infection/inflammation and that you together with ultrasound etc. investigations also should be given a very aggressive antibiotics treatment!