Hi,
Noted your history of discomfort in left upper breast, burning if lying in a typical position, itching and weakness.
The probable cause as per the history that you have provided are as follows:
Costochondritis.
Herpes zoster as itching is present and there may be rash one has to look for.
Nerve pinching with or without spinal problems.
Myalgia.
I would advise you the following in such a situation:
Consult your Doctor for proper and complete examination including inspection, palpation not to miss anything.
Mammography and
Ultrasound if something in breast is suspected.
Tests of blood.
Additional tests will depend upon the clinical findings.
And the treatment will be as per the cause thus found.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. T. Chandrakant, General Surgeon