I Get Really Nauseous Right After A Normal Bowel Movement

I get really nauseous right after a normal bowel movement and have to apply a heating pad for a half hour so I don't feel like throwing up. Also sometimes my heart starts racing like crazy and I'm so shaky if I have a bowel movement when I'm already feeling nauseous and I have almost thrown up. Any pressure to my lower abdomen including tight pants makes me feel sick. 4+ years now