My dad's in denial about his health. What can I do?

Hi All, I am at the end of a losing battle here and I am looking for some advice. My dad is 71 yrs old but a young looking dad who I believe is very very sick. Approx 2 years ago he started to lose drastic weight - he is 6ft 3" and used to be a 48" waist (weighing 20.5 stone) and is now a 32" waist (approx. weight is 10 stone) so as you can imagine he looks anorexic. All his bones stick out on his back/shoulder arms - face is sucked in etc. He very rarely eats (when he does its soft foods - yoghurts / soft biscuits / crisps / pancakes / fruit juice / segments etc). He doesn't drink at all but smoke approx. 20 a day. He has had a really bad cough for 2 years (worse now) he isn't spitting blood but his phlegm is dark grey and really thick. He sleeps now sitting up and has done for the last year, cannot lie flat as he starts coughing fit. Very grumpy and the minute I mention a Dr he blows a gasket. I have tried using dirty tactics as in if you love me you will see a Dr, I have cried many times infront of him, gone and googled (seems to be cancer most times) lots but nothing is helping me. I am so worried that one day I will get to his house and he wont be alive anymore. He is becoming very confused about certain things and forgets hes told me something but not to the dementia stage. I know that I cannot force my dad anywhere and afterall why would he go to a Dr when he hasn't been the whole time ive been alive - 32 years! Can someone pls advise me on what I can do or if there is something I can look out for. Ive tried all the excuses under the sun incl driving him to a and e but he wouldn't go in, tried drinks to fatten you up and he spits them out, tried lots of pasta - now refuses to eat it, etc. Please someone help me - I do not want to lose him and don't know what else to do, He is my best friend. Please help me or even give me some suggestions. From a very worried and concerned daughter