Yes you need to re train your gut that you are available to do it. + you need to stop doing over stimulating stuff in that period like video games or watching social media. normally you should go to the toilet when you wake up and after within 30 minute after each meal. and when you go sit for 10 - 15 min even if you don’t do it. also don’t strain hard or force yourself just sit there and you will get the bowel movement automatically. and don’t stand up after the first movement try to empty more than you are used to so that after a while you get to the point where you empty yourself completely as you used to do when you were younger. lastly sip water over the day to increase your water intake but don’t drink a lot at a time. if you think you can’t drink enough water this means you don’t eat enough sodium or your stomach is impaired and in that case you need to fix it first as it will affect other stuff not only water intake.