What's causes change in stool caliber? pencil thin stools different shapes and sizes always? did a colonoscopy and ends and capsule 4 months ago polyp non cancerous biopsies taken? should i be scared? been like this for years but lately really bad

Less worries please: Stool texture (regardless of volume or frequency of movements) , shape, & caliber are affected by multiple factors (fiber intake, bacterial load, GI transit, fluid secretion, etc.) Sounds however like your evaluation has been at least reassuring to-date.

Tight sphincter: While this is sometimes serious, a recent colonoscopy is reassuring. Try increasing the fiber content of your diet, fruits, vegetables, maybe a supplement like Metamucil (which is available at any drugstore). The usual culprit is a tight sphincter muscle and too little fiber in the diet.

Stool caliber: Are you constipated? That may change through life. Drink 2-3 liters water /gatorade juices milk, a day ( not just water will dilute sodium too much), also consider fiber like avocados, sweet potatoes, greens . Irritable bowel or stress can also cause GI dysfunction. F/u w/ doc