Can a 2-month-old baby have difficulty in passing stools due to infant dyschezia or Hirschsprung syndrome?

Hello doctor,

I have a 2-month-old son who had constipation three weeks ago after taking the vaccines. We took him to the emergency room after a week, and they found no sign of intussusception. The doctor advised us to give him prune juice. He had diarrhea for three days and is suffering from constipation again. It has been four days since his last bowel movement. He is constantly straining. We started stimulating his rectum 20 days ago. He was inconsolable today because he had no bowel movements, so we stimulated his rectum again. Every time we stimulate him, his bowel movements are normal. He is instantly calm and happy once he passes stools. I would like to know the following:

1. Why is he unable to pass stools without rectal stimulation?
2. Is he suffering from infant dyschezia again due to constipation?
3. Does he have Hirschsprung syndrome?