I've had my period for 12 days now. is this normal? i'm not on birth control nor am i pregnant. should i go to the doc?

Can wait a bit: The most common reason (after pregnancy) for a late or missed period is a late or missed ovulation. This is not strictly "normal" but it is very common, and is rarely to worry about if it doesn't become a pattern. You can certainly wait until your expected next period and see if it comes; if not, you may want to check in with your doctor. Good wishes.