First of all,breast pain is rarely associated with breast cancer. It’s true that most of the time painful breasts are caused by hormone imbalance and lumpiness is not unusual in young women your age.But there there are also other factors that could cause pain,such as nerve entrapment syndromes, disorders of the chest wall or ribs that can cause pain in the tissue of the breast as the only symptom.I agree that it's very important that you want to make sure about what is causing the pain you are experiencing.
I would advise you to consult a Breast Specialist as a first step and ask for an Ultrasound, if the test is negative,you can then see a Spinal Specialist and Neurologist as well who may run some type of testing to look at all surrounding bone structure, soft tissue, and nearby organs to rule out other underlying causes.
In the meantime, avoid caffeine and chocolate, reduce salt intake,apply warm compresses to the sore area. You know, diagnostics and treatment vary widely from physician to physician; it never hurts to get a second opinion.
Best wishes and hoping you’ll feel better soon.