I'm worried I may have lung cancer

Hi everyone. 

First I'd like to say that I'm extremely sorry if this post causes offence to diagnosed lung cancer patients. 

My name is Liam, I am 28 years old, father of 3 beautiful boys. For the last year I've been experiencing intense chest pains. Progressively over the last year the pain as got worse and worse. I suffer from anxiety and avoid doctors etc but I finally got the courage to go see my gp around 4 months ago. Most of the pain radiates on my left side. Which initially led me to believe I was having a heart attack. After several months of first experiencing these pains I figured out how to crack my sternum (thinking that my sternum was the pain) anyway I tolf my gp about this and got referred to MSK. I was told (without an xray or scan) that I have chronic costacondritus. I was sent for injections in my joints in my sternum to try and release the pain. Nothing worked. I told  my specialist several times that I feel like worse point of the pain is under my collar bone and above my top rib. But he was quick to go back to the costacondritus. For the last 8 weeks my left nipple has changed in colour. Im also experiencing a burning sensation in said nipple. It's very red and sore. No discharge however. For the last 2 weeks I've noticed in low light 1 of my pupils is larger than the other. I have a pain that goes down my left arm and I'm also experiencing numbness / tingling in my fingers on my left hand. I have smoked for the last 11 years regrettably and I have been working with metal for the last 12 years. I have a slight wheezing when I breath. I can clear this by coughing up phlegm which is a brown colour. I get extremely out of breath doing day to day things. So much that I can't perform in the bedroom anymore ( sorry if this is innapropiate) but I'm trying to explain best I can. I know it seems like I've read a list of lung cancer symptoms and just copy and pasted but I'm genuinely experiencing these. I've also noticed my neck is always slightly flushed red. I have frequent hot flushes also. I'm going to get back into the gp tomorrow and stress my case further. I just feel like I'm being ignored. Specially when I've been diagnosed with something without even having a scan or xray etc. Has anyone else experienced these issues? The reason why I'm so frustrated and worried about this is because most people just say because of age its highly unlikely. I've had this pain which is getting worse over time for a year. It's not going away at all. I'm just really worried. Thanks