Shortness of breath that isn't actually hindering your breathing (the feeling of constantly catching your breath) was my #1 anxiety symptom when I first started having panic attacks. Racing heart, also anxiety 101.
Does your shoulder pain get better or worse? What exacerbates it? I really honestly doubt you have lung cancer. You probably have anxiety, and either acid reflux (that can cause shoulder pain...and throat/neck pain...and chest pain...I ended up going to a cardiologist because I was sure I was having heart symptoms. I was not.) or muscle pain due to tension or something everyday like a pulled muscle.