Do you have hypothyroidism? Speaking from personal experience with hypothyroidism I've learn how it causes constipation. Also, for me, it made Mirylax and Linzess useless because it's a motility issue. It slows motility to an absolute crawl which leads to constipation. Once I went on synthroid my gut started to move again. My GI never connected the dots. I also learned that the muscles involved in having a BM get out of sync so they contract instead of relaxing when you try and go. They can be retrained.