Wendy - I perhaps didn't explain myself correctly.
When I mentioned pressure, i didn't mean to infer that you put the pressure on him - far from it - the fact is, like a lot of men, he may be putting the pressure on himself.
One thing about porn - apart from the obvious stimulation - is that it can give a man an inferiority complex! Usually, it's physically gorgeous people sending people into serial ecstacy .. except of course, it's not. It's professional actors who do this for a living, and can turn on and off their actions and reactions as soon as they hear 'Action' and 'Cut'.
Maybe your husband is setting himself goals he can't reach - obviously you will know this better than any of us.
The key is, communication. Expect him to be angry, because he is defensive, and that's a standard reaction, but try and get past that, and get into the fact that you love each other, and sex includes cramp, bummps, uncontrolled laughter, loosing the plot ... all the things that make us enthusiastic amateurs who do this for fun, and for love!
Talk to him. listen to him. Be patient, and you will get past this.