Were you sexually active and had unprotected intercourse? When was the last time if so?
The nipple discharge is hormonal and unrelated to pregnancy (not a pregnancy symptom but more a symptom of hormones out of whack). Being late or having an irregular period could also be a symptom of having out of sort hormones. Not too uncommon even if it has never happened to you.
So, when was the last time you had sex? We'll start there.