I could be anxiety, porn use, or a combination of both.
Here's a simple comparison test to check for porn-induced ED:
1 - Masturbate to your favorite porn.
2 - Try to masturbate using no porn and no fantasy - only sensations. Masturbate with same speed and pressure as you would during intercourse.
Compare one and two. How erect was your penis? How long did it take you to reach orgasm? What was your level of excitement? (A healthy young man should have no trouble attaining a full erection and masturbating to orgasm without porn or fantasy.)
If you have a strong erection on #1, but problems on #2, then you have porn-induced ED.
Number
If #2 is strong and solid, but you have trouble with a real partner, then you have anxiety induced ED
If you have problems during both 1 & 2, you may have severe porn-induced ED, or an organic problem. When in doubt see a good urologist.
These 2 Medhelp threads have lots of guys with porn-induced ED.
http://www.medhelp.org/posts/Mens-Health/22-with-porn-induced-erectiledysfunction/show/469209?page=1
http://www.medhelp.org/posts/Mens-Health/Too-much-porn-masturbation-causeED/show/183203
I suggest to GOOGLE VIDEO - erectile dysfunction and porn - and watch the video series.
Here’s a Psychology Today article on it
Porn-Induced Sexual Dysfunction Is A Growing Problem
http://www.psychologytoday.com/blog/cupids-poisoned-arrow/201107/porn-induced-sexualdysfunction-is-growing-problem