I am not sure, but your symptoms could very well be related to Radiation Therapy. I did not experienced what you describe, but each person reacts differently and I heard that some people do feel hot and cold chills following RT or Chemotherapy.
The most common side effects are skin reaction, mild fatigue and dull or sharp shooting pains in the breast that slowly goes away a few weeks or months following treatment.
You should mention this to the radiation oncology staff as well as the radiation oncologist since they are probably familiar with your symptoms, they may have suggestions as to how this could be better managed.
Hoping that your Radiation treatment will go smoothly without many complications.
Wishing you all the best...