It's always a good idea to see a good doctor to check for anything organic. However, urologists are completely ignorant of porn-induced ED. Sexolgists are also clueless.
Your brain has become desensitzed, as in an addiction process
I doubt that 8-9 years of smoking can cause ED in someone your age. If it's not some rare condition, then it's porn.
Check out this thread on medhelp- (you will see links there also)http://www.medhelp.org/posts/Mens-Health/22-with-porn-induced-erectile-dysfunction/show/469209
On our forum (and many other forums) we have been dealing with young men with ED caused by porn for years. They recover, but they have to quit porn. It usually takes 2 months -but it is highly variable process.
Google ***************.com and watch the presentation on "ED and porn".
Also watch the porn addiction series.
Go to the support page for more links. Also look at the Q&A, and you will see a few questions on porn and ED, with links, and many comments from men who recovered.