I've been with my fiance for over 3 years now and you know, for over the first year I was just too nervous/embarassed to be able to reach orgasm. But, over time, I forced myself to relax and it really does sink in! After a few months of telling myself to be calm, just enjoy it, don't be embarassed.. he loves me and my body... I now have an orgasm every time! It's wonderful!
So if it is psychological, you just have to train your brain, it will help. =) Positive reinforcement is a very powerful thing. Good luck with those O's and keep em cum'n ladies! har har
(Oh and once in a while I still masterbate to lesbian porn when I have the urge, since obviously my man can't provide that one thing hehe)