Runny Stools, Frequent Urge To Pass Stools, After Turning To Weight Loss Diet. Taking Lots Of Vegetables And Fruits. Advice?

I am trying to change my diet to help me lose weight. I have been juicing fruits and vegetables for the past month during the day and eating salads at night before going to bed. I have been having vary runny stools with no solid substance at all in it. And if I have a feeling that I have to go to the toilet I will usually have about 3 minutes to get there or it is hard to control. I am a 59 year old male and I weigh about 250 lbs. I have always had my bowel movements only in the mornings all of my life but now it seems that I have to go about 6 times a day and I am not eating heavy foods. I stopped eating meats, dairy, sugars, and starch based product such as breads, pasta, potatoes, and rice. I have lost about 25 lbs in the past 6 weeks but last week I went back to eating solid food to see if I would be getting solid stools again but it is still more like diarrhea . I drinks about a gallon of water a day to flush out my system and I used to pee a lot but now it runs out in my stools. Do you have any advice? Thank you, Gary