My period is a week late, and the over-the-counter pregnancy test is negative. I am in reasonably good health, and the only problem I've had in this area is that I don't react well to birth control medicines.

As . As doctors, the first thing we do when we hear that a young, 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. Unless you took the test in the last week, it may have been too early. A blood test can tell if you are pregnant as soon as 7 days after conception and a doctor's urine pregnancy test can tell if you are pregnant around when you next period should come. 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 are not pregnant and are still worried about an irregular cycle, give your doctor a call. Your doctor will take a thorough history and physical and may run some tests to find out why your period is irregular. Good luck!