There can be several reasons why you may feel pregnant, yet have a negative pregnancy test.
First, home pregnancy tests measure the amount of hCG in your urine. Some tests are more sensitive than others. Tests that are not very sensitive may produce false negatives as much as 25% of the time. If you suspect that this may be the case, a test taken approximately one week later can often show a positive.
A blood test is the most accurate way to measure hCG. Typically, this can only be done by your physician.
Hormonal imbalances or diabetes can have many symptoms that are similar to pregnancy symptoms. If you have continually tested negative but still have these symptoms, you should talk to your physician to discuss any other possible causes.
A woman's intuition is often more accurate than any test. At the same time, a strong desire to be pregnant can send a woman into a constant state of alertness, often causing her to misread impending menstruation signs as pregnancy symptoms. As frustrating as it is, the two conditions often produce similar feelings. Still, if symptoms are present, especially if you've missed a period or had an unusually light bout of spotting or bleeding, you should "act as if" and take good care of your body until you can confirm whether or not you are pregnant.