Dog shakes and shrieks in discomfort, we don't understand

Kermit, my dog had lived with us for 13 years and 8 months. He suffered from a feeling we do not know what. It hurts that we never had the resources (drive, much coins, time, transpo) to bring him to a vet clinic. I really feel bad everytime I think of those times that I did not do anything.

My mom was always the one who really gives him relief, generic and homemade meds, occasional professional vaccines, love, and care, and hugs, and kisses. She plays with him most of the time. My dad does all that, too, when he is home with us for work vacation. Kermit really became their second child after me.

Me? Hugs and kisses and birthday cakes are all I gave to him when I get home.

I regret that I assumed he is a super dog with a super strength (as super as me), that he'd made it through, that he'd live 10 more years on our side, even without a professional help.

Since he came (that was when I was 12), I have had him always in my plans, in my dreams. My dream to have a car is not for anything else but him, to bring him to places with our mom and dad. We always think about him. When we were out for lunch or vacation or what, it is the thought of him that makes us rush to get back home. He is sweet and lovely. When I am alone, I cry in thought of him. I always ask the day he'd come back.