I was 2 days late my last period but otherwise it was normal. 10 days after it ended i started slightly bleeding for 4 days. should i be concerned?

Breakthrough: This sounds like episode of breakthrough bleeding. Breakthrough bleeding is very common and happens to most women at some point in their lifetime. If it bothers you or concerns you you can always take birth control pills to regulate the cycle. Typically the problem is hormonal, but sometimes it's due to thyroid and or weighissues being too thin too heavy.

Not normal: Bleeding between periods is not considered normal. However in a young and otherwise healthy woman who has never had this before, i'm not very worried. As long as your pregnancy test is negative, i would not pursue it unless it happens again. At that point i would see your gynecologist for an evaluation. Irregular bleeding can be from polyps, fibroids, infections, or hormone changes.