When i defecate i find it hard to release stool ... half of the feces get released from rectum and when i try to release it re-enter inside rectum.why?

Rectal prolapse: Your symptoms are suggesting rectal prolapse that is essentially sliding of the lining of your rectum that is sticking out and than re-enters. Try to avoid constipation, make sure your thyroid condition is controlled. To avoid constipation remember that besides diet, hydration and physical exercise are critical. Do mention it to your doc at next visit.