Pomeranian Weight loss, lack of mobility

My 12 year old Pom "Buddy" has in the last 2 months lost a lot of weight. He is normally overweight. I believe because he seems to be having a hard time chewing (beggin strips, carrots, biscuits) that more than likely is why he "could" be losing the weight. But, I also have noticed he has more difficulty moving such as laying down and getting up. Several times he has gotten sick (white bile). Could this be simply old age with arthritis?
I feel bad because I just don't have the money to take him to a vet and all the tests. Any suggestions? I'm thinking more that he is simply getting old. My last Pomerania had to be put down when he was 13-14 yrs of age. I feel so bad but don't know what to do at this point? Thanks, Carolyn