Hi! If all tests are normal, then anxiety
could be the reason for excessive frequency of urination. This anxiety can in turn be further fuelled by your worry over the cause of frequent urination
You may need to see a Psychiatrist
for assessment of your anxiety and its treatment. Till you do so, you can try telling yourself that passing urine so frequently is not a consequence of a major physical illness BUT instead is a consequence of anxiety. Secondly, when you feel the urge to go, try and distract yourself by doing some work. Alternatively, you can set a minimum time frame before which you will not go to the toilet.