in case we haven't been introduced, I am Dany (frenchdude) from Montréal, Canada.
I remember you the most as I used to browse this site, just perusing the posts without ever having the guts to register. For some reason I remember your nickname (neckpain). It would be irrelevent to ask you what you suffer from, however, what I don't know is how it happened. As for me, 3 disc herniations did it. Probably at the gym where I used to train. Needless to say it's all history now.
As for your problem, I personally was on all sort of opioids including Methadone which is, in my opinion, the most constipation-inducing drug as of yet. And after a couple weeks of severe constipation, I was given ''PMS Docusate Sodium 100 mg'' to take daily at bed time.
You might have to Google it as there may be another name for that in the U.S. But believe you me, if this does not work, I don't know what will. It worked miracles for me where everything else had failed.