I feel so sorry for your dog and feel sorry for you. I know how this feels. We had to do this also 3 times.I know that you will miss him very much. Be sure that he is now on a place where he is not sick or has pain!!
Wonderful photo of your dog ,14 years is a long time for a German shepherd,but you can not miss hem,I wish you all the best for the next days or months ,maby years .RIP Jake.