I know that Paget's disease, which is a form of breast cancer involving the nipple itself, involves discharge from the nipple, but I don't know how it is diagnosed. Perhaps you could look into this. But would radiation to the area have anything to do with discharge? I didn't have a lumpectomy or radiation, so I don't have any experience...just thoughts.
I'm sorry you are having these worries. It is not easy, I know. I've had a couple of scares over the years, including a reported "mass" on a mammogram (not), a benign biopsy (thank you lord!), and being told that I had mets to the bones, which was not true. I hope this, too, is nothing.
Love and hugs...