Hi there, Erection and ejaculation are complex phenomenon enacted by our autonomic nervous system. To which the pelvic hypogastric plexus plays an important part. Being situated close to the rectum it sustains reversible injury in significant people who undergo surgery on rectum. However recovers in a large majority by 3 months. So t may sometime take even longer occasionally. You may see a urologist if it doesn't work even after 3 months.