I have all the symptoms of diabetes but blood test comes back negative. any possible explanation?

Depends on symptoms: If you have excessive thirst and excessive urination, it is possible to have 'water' diabetes (diabetes insipidus) rather than 'sugar' diabetes (diabetes mellitus); these require different tests. Some people with diabetes have weight loss, fatigue, blurred vision, extreme hunger -- these can be due to lots of things, but thyroid, blood counts, and iron should be checked. See an eye dr.