Don't be self-conscious about offering your own ideas about your condition. Often the patient is the one who discovers the cause of his illness. We live with ourselves every day. There is plenty the doctor could miss that does not show up on a test.
I am lucky in that I have two fine doctors. They listen to what I have to say and, because of that, my treatment is excellent. By the way I have diagnosed myself correctly.
First of all I would advise you to ask your doctor for a referral to see a Breast Specialist and have this lump in your breast further investigated by having an Ultrasound/ MRI or whatever test the doctor will recommend.
The pain you are experiencing could be due to many causes,other than breast cancer, such as Costochondritis,pinched nerve,pulled muscle, etc..
If tests show that you don't have a breast problem,then you should pursue this matter until you find out what is causing the pain you are describing.
I posted a comment about burning pain, I just want to add that I been having this pain off and on since May 2012. I want to something called a PET Scan or MRI, some test that could help see whats going on with me, can I request these type of tests or what? My shoulder is hurting now and tender pain under arm close to breast. After telling my doctor and the hospital about pain in breast also none of them felt for any lumps or bumps, I did my own breast exam and just at the outer edge, I feel a sore spot and lump the size of un popped kernel of corn, sorry I can't think of anything else to describe size, it hurts to touch it. The mammogram was done just over a week ago, and have not heard anything, so it will probably come back normal. Would a Ultra sound or any of the other tests I mentioned help with detecting anything that small?