How can I retrain my body to not hold in my poop anymore? ?

Stimulant laxatives are very bad for your body, and not good to take more than very occasionally. However, Miralax is a non-stimulant bulk adding laxative that can make it easier to use the restroom. It is a flavorless powder that dissolves in any liquid, and it takes a few days to work. Sometimes when you are constipated the really hard poop doesn't come out, and fluid builds up around it, leading to what appears to be loose stools and that "still full" feeling. I would also recommend getting a footstool and placing it in front of your toilet. When you use the restroom, put your feet in front of you on the stool and lean forward, so it's almost like your touching your head to your knees. This is a more effective angle for the rectum. Also, you might want to see a doctor. They might be able to figure out why you have this problem in the first place. Good luck!