My 18 year old Jack Russell is losing a lot of hair. He has been dewormed and is eating although not as much as he used to. He has started to lose some weight. He is still a bit active with bursts of energy. I need to know when to make the hard decision of letting him go. I really dont want to let him suffer and he is such a brave dog it is difficult to see when he is uncomfortable sins he hides it very well. I dont know what to do.