I am so sorry Loreta, this is never an easy decision, but it sounds like it is the best for Blacky right now. Take heart in knowing that for 4 years you gave him a home, a family, and lots of love, and that now you are choosing the appropriate way to end his suffering. And he departs having known a different/better way of living because you took him in. Big hugs to you, big hugs to Blacky, and may his transition be swift.