dyeing dog - naturally or put down

My dog is 17 and he is dying. He had a seizure about 2 months ago and the vet never could tell me why he had it. He has a slight heart murmer but stopped eating normally after the seizure. Last week he totally stopped eating and has gotten down to skin and bones. Ive treid keeping pedialite in him and he to the point he cant move now. I try to keep him mouth hydrated with water in a straw but every 1/2 hour he starts to yelp until i pet him and change the pad hes laying on if he has peaed. Is he in pain or is he just wanting to be held? If he is in pain, I need to have him put down but it is killing me just thinking about it. And if I pay for advise, I wont have the money to take him in to the vet. Should I let him go naturally and how long will this take. He stopped drinking water on his own about 3 days ago, Can someone help me?

I am sooo sorry you and your dog are going thru this. It is so hard losing a pet.
   
I have never had to put one down. I can only imagine what you are going thru.
   
I would not want the dog to suffer. If the vet says there is no hope for him to regain his health and he/she is suffering, then it would be in his best interest for the suffering to end. Keep his as comfortable as possible and get him to a vet! I'm sure they will allow you to make payments to them. They don't want animals to suffer either.
   
I realize this is a very difficult time. Do what is best for your dog.

That's the main question. Do you think he is in pain? He stops yelping when I pet him almost like hes saying is someone here with me? His eyes are real bad so he hasnt been able to see good for almost a year now.
   
Thats the problem, if he were in pain wouldnt he cry or wine? And if he's not in pain, should I put doen a dog that has been trying so hard to hold on?
   
After all, just as Ive been with him, Snowball's been with me for 17 years too.