In the bedroom, as in life, sometimes you have to fake it. Until you make it. You know, go along before you get along. Go through the motions and whatnot.
This applies to men and women (as well as dudes and chicks), in and out of the boudoir. Even the most self-confident dude knows at some level that every roll in the hay-hay-hay-hay ooooo-oooooh-whoa (like in "Don't You (Forget About Me)" by Simple Minds) does not end in his partner having the big O. Evidently, this is of great consternation to women. Lemondrop has a great "how to" come clean (heh) about the duplicity of faking it. Guess what? You don't have to.
Even the least skilled actress in the female population is probably convincing enough for all but the dude from Lie To Me to be duped, so why spoil the charade? Short answer, because you want to have actual orgasms and lying to someone you may or may not love eventually eats away at your body, mind and soul. Good rationale, doubtless. And you should tell and you should give him some pointers on what you actually like. If he's not a real jerk or a crybaby he'll appreciate the straightforward manner with which you do business and your refreshing honesty and be willing to do whatever it takes to make it rain*.
But sometimes you gotta fake it. You may have one of those guys who take every failure in that department incredibly personally (this is far better than the opposite guy**). This guy (and every other guy) needs a bone thrown his way every now and again. For instance, if things are just not happening on your end, a little fakeroo will let him know it's OK just to finish.
Guess what? We do it too. While it takes a dandy sleight of hand for a man to fake orgasms (even if he can make faces like "J**z In My Pants"), we fake plenty of other stuff. For instance, not that many guys like to talk about feelings or how their day was. And almost no guy under 50 really likes going for walks. But we pretend to. And we pretend to like outfits, hairstyles and food that we absolutely don't understand. TI probably knows this better than anyone, "and we can do whatever you like."
Part of being a decent member of society (and a relationship) is the implicit understanding that you're going to have to pretend to like some things to spare people's feelings. The best you can do is smile as much as you can and let serotonin (or Calgon) take you away***. But seriously, don't overdo it, Meryl Streep.
*Note: That may have been from Nada Surf's "Popular."
**Note: Guys who don't care about your level of satisfaction make jokes like, "How can you tell if a woman is having an orgasm?" And answers themselves a half sec later, “Who cares?”
***Note: Only young children, the elderly and the mentally infirm get a pass on being nice, everyone else gets labeled an ice-hole.