Customer, I would be happy to assist -
1) are you having any cramping with these bleeds? Any pain?
2) are you sexually active? Any unprotected sex in the last few months? are you on any birth control?
My number one guess is that you got pregnant and are having a miscarriage now. At your age that is the most likely explanation. An over the counter pregnancy test, if positive, would confirm this.
I hope this answer helps. If you need any clarification or have any other questions please feel free to ask. If you are satisfied with my response please click 'ACCEPT'; bonuses and/or feedback are most welcome. Thank you and good luck!
There are other possibilities... but miscarriage is #1,2,and 3 on my list given your age. Even if you are miscarrying the pregnancy hormone will be high enough for the urine pregnancy test to pick up on.
If the pregnancy test is Negative, then next on my list (#4!) is that you possibly had an irregular cycle that is causing you have prolonged withdrawl bleeding. If this is the case, giving your self some progesterone for a week or so should stop the bleeding. If your pregnancy test is negative, this is probably what is going on. Your obgyn should be able to provide you with a short term prescript for this.
I hope this better answers your question =)