Bad news about dog

Found out this week one of dogs has Lymphoma, his breathing has gotten heavier so took him in. Both my dogs were just at vet for yearly at end of April. They did test him for cushing disease, but that came back good. Then they wanted to test him for thyroid but I declined, but that would of came back negative because it wasn’t that either. He’s 14 so not going to put him through chemo him to be around 1 more year. He’s on meds but that gives him 2 to 3 months. I was up after 5am with him this morning because of his breathing, thought he might pass but he’s still handling in there. I cried, I don’t think his passing would hit me as hard as my cat because he’s family dog and my cat was just mines but that might not be the case. He was originally my sister dog, both dogs are but we keep them when she moved out and because she lived in apartment and her schedule was all over the place. She hasn’t really helped out probably just once or twice in beginning but that’s it doesn’t even offer help even when she is the only one available to take them to vet me or my parents have to give her money or call in payment. She did move back in but I bet she doesn’t offer some money for cremation. Anyways I’m trying to prepare myself I might wake up to dead dog or come home to one. My cat died early morning so I was there, I don’t know which will be harder. I bought a mushroom herbal liquid from Pet Wellbeing off Amazon that’s suppose to help, it’s suppose to get here this morning so I’ll see because at this point I’m thinking August for him to stick around unless his breathing gets worse then will have to put him down. 😔😢💔.