Pomeranian vomiting and diarrhea

My 14 year old Pomeranian has been experiencing diarrhea for the last month or more. Some days he goes several times and others not at all. He has also been vomiting, but it's mostly a small amount of white foam. Occasionally he will throw up his food. Most days I can't get him to eat dog food. I've tried wet food and dry, but 90% of the time he's not interested. I've been giving him boiled chicken breast which he LOVES just so I can get him to eat. He's also lost a lot of weight in a short amount of time. Some days he's entergetic like a puppy and other days he's very lethargic. Those are the days he vomits. I'd say it's maybe 70/30 with 70 being good days. I took him to the vet but they don't know what's wrong with him and I can't afford to spend thousands of dollars to figure it out has anyone else had similar symptoms or experiences with their dog?

Have the vets suggested a blood profile and a urine test. It shouldn't cost a fortune, and should help them come up with a diagnosis.

Was it bile vomit because he is hungry , is he OK now.