Hello,
Most home pregnancy tests that check urine beta-HCG are sensitive to 20-25 mIU/ml of HCG. The test can be positive anywhere from about 2-3 days prior to a missed menses to 4-5 days after, but usually it should be done 7-10 days past your missed period. There are a number of variables which will affect the accuracy of the pregnancy test, and these include: the days of a woman's menstrual cycle and ovulation can change each month, the exact day of implantation of the fertilized egg is not always known. It is not uncommon for women to have negative pregnancy tests when they are pregnant.
Hence it is better to get serum HCG levels done.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
some women miss there period it totally normal trust me. i would like to think that its just giving you body a brake. i know from experience. but if your still think your at risk here go something that could help you understand your body a little better http://www.mypregnancybaby.com/reasons-missed-period-not-pregnant/ its easy to read and not a lot of text.