Extreme pain in breasts. could this be a sign of breast cancer or something else?

Unlikely : Pain is usually not the presenting symptom of breast cancer - unless the cancer is advanced and growing through the skin. Breast cancer mostly presents as a palpable lump or a mammographic finding. See your md for a good history and physical. Ultrasound, mammogram , or MRI could be indicated if there is a suspicious finding.

Cystic change: Fibrocystic disease/changes is very common in women. This is most often seen during the menstrual cycle. Breast feel lumpy and painful which is caused by cyst formation (fluid filled areas) due to hormonal changes. Some women may have these changes without being on their menstrual cycle. Caffeine may cause the cysts to be overactive resulting in pain. This is not related to cancer.