One of the most frequent threads on AB concerns porn, and differeing attitudes to it, which provides one of the biggest gaps in understanding between the sexes.
OK wendy, first things first - it's not a matter of 'either or' with sex with you, or porn, it doesn't work like that. Men get entirely different pleasures from both, the fact that your husband enjoys porn does not directly indiciate that he prefers it to you.
The simple fact is, masturbation is a purely selfish act, you get to please yourself entirely in terms of stiumus, time taken, etc. and this is a large part of its appeal.
Sex in a loving relationship is entirely different - and this may be the root of the issue.
In a loving relationship, a man should be trying hard to make sure his parter is enjoying the experience, and this takes time, concentration, patience, and giving - something men do not always possess in great quantities!
Your husband may simply feel that he is not 'performing' properly, and rather than address the issue with you, he is simply absenting himself from the situation.
You need to have a talk wtiht him, and take the pressure off.
Start by assuring him that making love is not a contest, and an orgasm for either partner is not the 'gold medal' result you have to work towards. That should reassure him that he is not being 'monitored', and he should be more relaxed.
Encourage cuddling, simply to get some intimacy back, without leading to sex. This should ensure a more open expression of feelings between you, bot physical and verbal, and hopefully this will ease you into making love together again.
You may both benefit from some counseling from Relate who have vast experience in dealing with the issue - which is extremely common - and the two combined should get you both moving in the right direction.
Good luck,m and keep us posted.