What Causes Urge To Urinate But With Little Urine?

I am a 77 yr. old female I drink fluids all day. I have the urge to urinate,but I do not empty my bladder. I used to urinate fully 2times a night. Now, the flow is limited. I have no symptoms of a UTI. I have vasculitis and dysautonomia and neuropathy this decrease in urinating started about 6 weeks ago. I am on5mg of prednisone and ave been on a variety of doses for 4 years. My creative level is a little low