My 15y.o. Lhasa usually walks over a mile a day and 2 days ago he stopped walking. He urinated outside like a female dog and this was the dog who for 15years lifted his leg 20x on a 4 block walk. He vomited once and is drinking water. I force fed him a small amount of food. He is very lethargic. He did not injure himself. Just suddenly cant walk he tumbles over and wont lift his leg. He urinated on himself while sleeping. Anybody know what could be the cause? I will take him to the vet but, cant afford thousands in vet bills. My last dog died a year ago of cancer and I spent about 3,000 on chemo, test, removal of a salvitory gland. etc