I had been with other partners, masturbated, tried vibrators, plugs, all sorts of things, and still nothing. I'd actually given up on ever orgasming. We currently have sex infrequently (once a month), but when we do, it is wonderful - a bit too long for me because I get tired - but wonderful and pleasurable.  Still, I have never orgasmed since that one time. 

For some reason, in the past month, my libido has been out of control. I think about sex all of the time, and so I've started regularly masturbating to help take the edge off. I would really love to orgasm again, but I never seem to come close. I have a finger vibrator, some porn, have read books and videos, but no dice still. Please help. I feel in desperate need for some relief and I don't know what to do!

Since you had one orgasm, we can probably rule out any physical problem. However, since you tried all the standard methods of having an orgasm, and have read books on the subject, there is no magic bullet that I can give you via this forum.

I think you can be helped, but only if a sex therapist has the opportunity to take a complete sexual status exam, in other words ask you a lot of questions about your sex life, and gives you homework that you can report back on. You seem to have some psychological block, but figuring out what will help you get over it will take a fair amount of back and forth between you and a sex therapist.