A similar change happened to me a few years after I was diagnosed with Crohn's. At first the constipation episodes would be rare, perhaps once every few months. But pretty bad when they did happen - it was as though my bowels would just seize up and stop working for a few days. The longer I couldn't go the harder and more painful my stool became to pass. After one appalling episode which was so bad, I ended up in A&E (the less said about
that, the better), I began to use Miralax to soften my stool: if that failed, I would use a glycerin suppository. Grim, but it worked.
Gradually the constipation episodes became more and more frequent. At the same time my Crohn's disease was also getting worse. I developed a stricture and perhaps that caused the constipation. Except that the stricture wasn't diagnosed until long after the constipation began, so I don't really know.
Most of the time alternating diarrhoea and constipation is a symptom of IBS, but as you have Crohn's disease and the change appears to be fairly sudden, I would get it checked out. It might reflect a change in your disease.
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)