So, I had this many moons ago and it was a hormone imbalance. They checked me for a small, non cancerous tumor in the pituitary gland as that can create this situation of prolactemia. I didn't have it. So, we then looked at my hormones. I had a natural excessive production of estrogen.
So, talk to your doctor about this as you likely have one of the above two scenarios. Let us know!
Have you tried not squeezing the breast for a while? You might be stimulating production.
See your doc also, and get your prolactin levels checked.