In spite of what you've described, what's his quality of life like? 14 is almost 100 in human terms so I think he's entitled to have a few wee ailments, don't you?
But does he still have a healthy appetite? Can he still make it out for a leisurely walk? Does he greet you when you come home?
If the answer to these questions is "yes", then his symptoms appear to be nothing more than old age.
You know, most pets can 'tell you' when their time's up, and heartbreaking though it may be, the kindest thing then is to let them go, as gently as possible, by biting the bullet, taking them to the vet, and unless the latter gives you a very good reason otherwise, then have the 'dirty deed' done but stay with them while it happens and comfort and reassure them - it's the least they deserve after the years of love and loyal service.
The worst thing, though, is to try to keep them going just because you can't bring yourself to have them put to sleep - their quality of life is the paramount thing.
I wish you the best at this very painful time.