I'm sorry to hear you are worried about Rory
Has he been to see a vet at all?
At his age, and with these symptoms, there are many things that could be going on with Rory, such as diabetes, pancreatitis, ongoing tummy bugs or more serious issues. He could also have some arthritis or some senility issues going on.
Many of these issues are very treatable once diagnosed. I really think that the best thing to do at this stage is to take him in to your vet for a health check. They may reccommend a blood test to screen for some common problems.
At home, if he is still being sick, then I would recommend sticking to quite a bland diet, ensure he is up to date with his worming treatments, and constant amounts of gentle exercise to keep his joints loose.
I hope this helps and please ask if you have any further questions.