Hello,
Welcome to ehealthforum and I am really glad to help you.
A milky,watery discharge from the breast is common due to mild hormonal changes in the body.
Chronic breast stimulation, such as from frequent breast self-examinations or sexual activity,taking medications as hormonal pills(you have taken i pill)also is one of the common causes of galactorrhoea.The other possible causes are mammary duct ectasia, an underactive thyroid gland, tumor (prolactinoma) or other disorder of the pituitary gland, etc.
All these causes can be ruled out after some simple blood tests and a detailed examination from your gynecologist.
You can wait and watch for 7-10 days for it to subside spontaneously and if it persists then the cause needs to be investigated.
Take care!