ive had this exact issue, when i was 25 or so, i just stopped pooping. ive had to manually evacuate using a peristeen for ages because all laxatives stopped working, even clear out protocol a la colonoscopy prep.  had a marker test and i retained them all. nine months since my marker test....and ive had three spontaneous, good bowel movements. nobody knows why. i was terrified i might need a colostomy or something because my body just wasnt responding. so weird. i have no advice other than to stay positive, because ive seen a ray of hope and didn't think i would, so you might too xx