My earliest recall was age 5, and the reason I remember is because we were at the shore for 2 weeks and my mom kept giving me castor oil because I hadn’t had a bowel movement the whole time we were there. As far as my stomach, it just gets very hard and bloated, as an adult I have gone as long as 2-3 weeks without a bowel movement- so bad that I get to the point where I can’t urinate because I’m so blocked up. I’m 68 now, so I’m very used to this, but I sympathize with you because of how uncomfortable and embarrassing it can be.