Hello!
I am no expert, but I do agree with Admirer regarding the fact that your bf is used to watching porn. that's all there is to it. He ought to stop watching porn and maybe even stop masturbating on his own. Since he is relatively young, it'll be a challenge for him to stop masturbating for a week even, but if he achieves this, you'll be able to make him *** in no time.
If he doesn't even then, or if he isnt able to stop masturbating, he ought to seek medical help (either doctor or psychiatrist)
Take care
Don't dominate him, let him use the muscles around his pelvic region. Its important because he can't ejaculate unless those pelvic muscles are not in action. If he really love you ask him to stop watching porno. If he can't ejaculate then its better to end sex without ejaculation. Its not your fault, his ejaculation is linked with porno. Its kind of a stimulus for his ejaculation. Unless he don't get rid of porno, doesn't seem like he can do well. He needs to see a psychiatrist. Thank you!