I'm terrified of my dog dying

Ladies I really need some help. My dog is honestly my best friend and I've grown up with him but now he's really old and he's only a small dog. He's fine during the day but at night he seems to struggle so much and every night I'm afraid I'll wake up without him. We have zero money and can't take him to the vet and haven't since he got desexed like 10 years ago but I'm so scared of losing him and I don't know what to do.