You've gotten a lot of responses here and at least a number of them have been anywhere from stupid to downright harmful. We're all just randos, so hopefully you've taken everything here with a grain (or mountain) of salt. I don't know where you live but there may be opportunities to move for treatment and I advise you look into them.
Do not fall for the homeopathy bullshit. Just don't. Don't even consider the route. Research everything, demand double-blind trials and empirical evidence. Speak to as many accredited doctors as you can, if possible, and explore your options. Lung cancer is pretty aggressive but not unbeatable-- getting sidelined on your treatment by delaying yourself any longer or by following some of these wack suggestions of others will definitely not help you live, and they may just, in fact, get you killed.
It might be easy to feel like you're out of options and time, and maybe at some point you will know for sure that that is the case. But until then, push, push, push. Fight. The options are out there, and your attitude about it is most of the battle. If nothing else then at least at the end of it all you will know that you've done all you can, and you won't be left wondering how much of your life you threw away because you were too dumb or anxious to act more decisively a little sooner.
You can do it, op. You fucked yourself over in the first few battles by pretending there were no battles at all, but the war is just getting started. You've got this.