Hello, i'm not sure whether this is what i have. i am only 17 and i realised a line of red little dots (like bruising) across my left breast?

Monitorforadayortwo: Without more info it's difficult to speculate. Is it possible that they are just marks left from a poor fitting bra? Do they hurt? Are they raised at all? Dots or small red bumps? In the face of just little red dots, I suggest just monitoring if they don't go away in a day or two, or if they change then get them looked at.