10 1/2 year old Pom not acting himself

My dog was recently diagnosed with an ar infection as well as arthritis. I took him to the vet and he was prescribed meds for ear infection and Rymadyl. I gave him all of the meds for ear infection and Rymadyl for about 20 days. He still was not acting right so I took him back to the Vet on 07-04-11. The vet said tha he got into something and that he need to put him on IV. He was given antibotics and released later that day. I have since stopped giving him the Rymadyl because of concerns that I had read about on the internet. He is still not acting himself. Someday he acts better then others. Could it be possible that he is acting this way because he is getting old and does not want to be bothered or could it be some health issue. Oh and he no longer wants much to do with me just my husband. I have been the one that has had to give him his meds and ear wash.