Metamucil and miralax (polyethylene glycol) wont help with constipation. What's next?

Fiber supplements. Require time and plenty of fluids; otherwise, they can add to the constipation problem. Are you taking any meds that might cause constipation (narcotic pain meds are notorious for constipating). Have you used laxatives for a long time? See your fp/pcp for further advice.
Constipation. Time to see your doctor. There are other options but first an evaluation as to the cause of your constipation is essential.