(NSFW) Why do I have to use the washroom just as I stand and get dressed?

I have the feeling to go and I do but It never quite finishes and, I have to go again often just when I stand up for bullet diarrhea. ( liquid and solid at the same time). I went to the doctor and had a physical and everything was perfect except I had moderate cholesterol. He suggested that I have more fiber and more salt and take it easy for binge reading. What do you suggest? Maybe walking more? Also I have to pee every 15 minutes, except at night where I can wait a hour before needing to pee.