Thank you for the query.
If you are around 50, you should have colonoscopy
performed as such symptoms can be in early colon cancer
stage. Especially if you also have some blood in stool
or lost some weight recently (at the age of 50, colonoscopy should be performed even if there is no symptoms at all).
Moreover, you should know that plenty of mineral water intake (2-3 l/24hours), especially well mineralized, can cause constipations.
Hope this will help.