Yes, I know exactly what you are going through. The only difference is that my husband is the one with lung cancer.
His cancer has spread quite rapidly. He just finished a round of radiation on his brain. I too am the only caregiver. We have three sons, but they work and it's difficult for them to help me. I stay on the job 24-7 just like you do, and often feel like crying. Going to mass helps me along with exercise. There is not much help in our community for cancer patients either. They just shut down the nurse's station so we have to drive into Miami; 80 miles each way everyday. I am exhausted. The American Cancer society sent a gentlemen to help with driving. He's not too alert, and my husband ended up in Fort Lauderdale when his treatment is in South Miami.
Hang in there. The Harvard Medical School informed us there are new drugs for lung cancer coming out next week. They will help our loved ones with a better quality of life. Bless You.