Cause of frequent urination? negative for uti, diabetes, negative blood test, and negative ultrasound?

Frequent urination: Assuming you have no symptoms of burning on urination or pain, causes to consider include small bladder syndrome (some people's bladders are just smaller than others) or interstitial cystitis (but usually associated with significant discomfort). Certain vaginal infections (notably herpes, but also yeast or gardneralla) can cause frequency, but also usually associated with discomfort.

Need more info..: This, without other symptoms and/or signs, is a nonspecific finding. It could be stress, or anxiety. It could simply be from drinking too much fluids, or coffee and/or soda. It could be nothing. It would be a good idea to wait a few days and try to relax, and if it persists, see your doctor for further work-up along the lines of possible urinary incontinence.