My 18 yr old daughter has had her period for the last 10 weeks,she is in huge pain and lots of headaches,what could it be and what tests should she have done.

She should have seen a doctor by now, your regular family doctor, who may or may not have referred her to a specialist such as a gynecologist. There are numerous possibilities from fibroids to thyroid problems. I'm wondering why you are asking about what tests to order after 10 weeks of suffering. You don't order tests; the doctor does. Is because she doesn't have insurance? Find a walk in clinic, or pay for it.