Hi and welcome,
I too have stage 4 lung cancer and can relate to ur fear, anxiety and pain.
Pls talk wth ur treating team about ur concerns and pain - they prob will have some ideas.
I'm not sure of ur treatment for chemo - I had 2 types carboplatin and germocitin (im guessing on the spellings). Chemo often makes u fatigued and short of breath so it may be that..... During chemo I had back pain, chest pain, kidney pain and pain under my rib cage. I was prescribed oxycontin to assist with pain from my oncologist.
Stage 4 doesn't mean the worst case - I'm still here 14mths on. So don't give up hope, think positive when u can, laugh, live and love :)
What works varies for individuals - I spent time in fresh air, did meditation and deep breathing, laughed, cried and sometimes just worried.
best wishes ,
Rubes