My period is 16 days late, and i tested negative 2 times i am 19 years old

As : As doctors, the first thing we do when we hear that a fertile woman is having a missed period or abnormal spotting, we check a pregnancy test. You can either take a home pregnancy test as long as it has been 5- 6 weeks since your last normal period, or you can go see your doctor and they can test you. A home pregnancy test is 97% accurate if taken a week or more after the missed period. Did you wait long enough for your pregnancy tests to have been accurate? If so, 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 you continue to have an irregular cycle, you should give your doctor or your ob/gyne a call. Good luck!

Late period: Reasons for missed / late period include: an anovulatory cycle in which no egg is released, marked v or ^ in weight; eating disorder; Over-exercising (endurance athletics), stress, travel, significant illnesses, oral contraceptives & other meds, Illegal drug use, breast feeding, hormone imbalances and medical problems (i.e., PCOS). Pregnancy is #1 reason.