Can chronic stress/anxiety cause bowel problems? i have been constipated since three weeks. soft stools, but need to strain often. sometimes narrow stools. also, feelings of incomplete evacuation. can this be caused by stress?

Yes, it can.: A young adult with constipation needs to be sure there is no other disease causing it. If constipation is just due to slow movement of the food and poop through the gut, then things people try are vegetables, water, fiber-plus-water, prune juice, prunes, polyethylene glycol, Senokot or other senna, milk of magnesia, other laxatives... One's doctor may evaluate and consider other medication.