Period is 15 days late?

Im 14 and my cycle has been pretty normal sometimes skips a month but usually its comes about like 4 days late or something . but its never been so late. I had my midterms so it might be stress but i dont feel stressed out. I was due on the 18 and i got a few spots but it never came also some back pain. Ive been getting a LOT of discharge later but still noothing. And no im not pregnant im a virgin. Im getting kinda worried . Please help.