When I defecate, I have a lingering burning sensation as if I still have additional waste.?

Maybe anal fissure. Pain or burning sensation assoc. W/ bms can be associated with an anal fissure. Typically located posteriorly at the end of the anal canal, they are not easily seen on colonoscopy & even direct visualization can be difficult. Increase fiber & bulk laxatives and topical Diltiazem 2% ointment can help. Can require surgery. A colorectal surgeon can help. Fascrs.Org/patients/conditions/anal_fissure.
Many possibilities. Constipation (or just incomplete emptying which is essentially constipation), hemorrhoids (very common), parasite/worms (less likely), rectal prolapse (rectum trying to exit via the anus). Don't strain or grunt, eat lots of fiber, drink lots of water and have your doctor evaluate this.