My doctor is testing me for a pituitary tumor because of breast discharge but nowhere near pregnant or recently pregnant, is this normal?

Yes: The pituitary can produce a hormone called prolactin which can stimulate lactation.

Yes: Sometimes an abnormality in your pituitary will lead to increased levels of prolactin. Increased prolactin can lead breast discharge.

Common: Nipple discharge is relatively common in women. A pituitary tumor producing prolactin is one of the causes, although a rare one. Your prolactin levels also could be checked.