My periods come like clockwork every 25 days, ever since I was eleven. This month, however, I am 5 days late. I have all the signs of PMS -- mild (very mild) abdominal discomfort, lower back pain, moodiness, light headedness -- but with frequent headaches and nausea. I took two home pregnancy tests (one the day of my expected period, and one the day after) and both were negative. However, I'm five days late and still no period. There has been no change to any eating/sleeping habits, my stress levels have not increased, and I have not been sick. Are the tests wrong? Or is there another reason for my late period?

I am no expert but we did a lot of reading on the subject when we were trying to get pregnant.

You can frequently get false negatives if the hormone level is low enough. You will very rarely get a false positive.

See your OBGYN. He will do a test where he measures the hormone level one day and repeats it I believe 2 or 3 days later. If there is a significant increase, you are pregnant.

False negatives are common for several reasons. The number one reason is not taking the test using first morning urine.

I'd give it another week and see if your period is just late... it happens sometimes. Try another test at that time if still no period.