What Causes White Milky Discharge From The Breast?

hello. Im a 21 year old female. My right breast is secreting a white milky substance when I squeeze it. I noticed this a 4 days back. I also have a persistent itch that takes hold of thighs back breast and stomach area without any rash. Im not sexually active so I ruled out pregnancy. What can be the causes? My GP said its normal but Im not fully satisfied as he didn't run any tests.