Hello,
First of all,mammary duct ectasia has to be ruled out. It causes one or more of the ducts beneath your nipple to become inflamed and clogged with a thick, sticky substance.
Second possibility is of galactorrhea which is a feature of hormonal imbalance, such as from taking birth control pills,an underactive thyroid gland tumor (prolactinoma) or other disorder of the pituitary gland and chronic breast stimulation, such as from frequent breast self-exams or sexual activity.
Third possibility is of intraductal papilloma.It is a small, usually noncancerous (benign) growth that projects into a milk duct near your nipple.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
That is a big enough red flag to send you to the doc. Please see one as soon as you can.
Also, it's usually only from the bigger breast. I rarely get the white stuff on my other side.