When im on a period I pass atleast 12 large blood clots?

Not normal. Passing a lot of blood clots while you are on your period isn't normal. I would definitely recommend you see a gynecologist and discuss this. Could be due to hormonal issues, thyroid problems, weight issues (thin/heavy). But that seems like too much bleeding for someone your age. Rarely heavy menstrual bleeding due to vonwillebrand. Get a check up so you'll know. Take care.