Constipation and stomach not being clear

I am 26 year male. I always feel constipated. From last 10 years I never felt my stomach being cleaned thoroughly while going too loo. I have tried many medicines some on suggestion of Doctor like dulcoflex, caster oil, isabgol, looze and numerous other medicine. But never felt that I got clear poop. I consumed pa top dsr for 20 days but no benefit. Sometimes when there is excessive gas formed in stomach then it feels that gas is moving in my back and legs. It feels very severe pain. Sometimes I have to bind any cloth tighten so that pain is limited to a particular section not whole body. I have also problem of anxiety and undergoing treatment of that. I also got thyroid and ultrasound done but nothing in report. What is this problem. Always feels vomiting like whenever I see oily foods.