Slim belt n pull belly inside. Stomach?

I have used slim belly belt for 1year before 4years. Since then sucking or pulling my belly inside to look slimmer became my habit not knowingly. I had loose stools problem from them daily 3,4 times. Ibs symptoms Now i realised that because of this i got these loose stools. I think i completely strained my stomach muscles all day. Only i relaxed stomach is in night time while sleeping. I tried stopping sucking my belly inside, instead pushing my belly out forcely now to counteract this effect . But cant push whole day my belly out. I forget or less energy. loose stools improved little. But not fully recovered. Some times without knowlingly i do sucking belly again. I get loose stools again. I cant do stomach exercises or dips which strains on stomach. I get stomach pain after workout and while passing stools next day. I stoppped all stomach workouts. I have done abdominal ct. Colonoscopy. Endoscopy. Everything is fine. Can anyone have idea what might happened inside stomach??