Check driveshaft, carrier bearings, and u-joint(s)

I suppose the clutch may be worn. It would be more likely that the secondary drive belt has a problem or you lost a tension spring.

I can't get the PTO on my 425 John Deere to shut off, Any ideas of what I can do to fix this?

You will have to verify if there is power to your clutch in the off position first to determine if it is electrical or something physical w/ the clutch.