My cousin doesn't have her period for months at a time shes 17 why is that and recently she has had liquid coming out of her belly button what is that? also she has not had sex ever so we know she isnt pregnant

Many : Many women will have an irregular cycle for the first 2-3 years after they start their periods. This is completely normal and will improve as she gets older. If this is not the case, there are other reasons besides pregnancy that can cause a woman to miss a period such as: stress, diet, excessive exercise or a hormone imbalance such as with a thyroid disorder or polycystic ovarian syndrome. If she is not pregnant and is still worried about an irregular cycle, she can give her doctor a call. Her doctor will take a thorough history and physical and may run some tests to find out why her period is irregular. Good luck!