Let's say he's been going down on you for a while and it feels...okay. At least he's trying. Might as well reward his efforts with a fake orgasm, right? Wrong! Big mistake, missy! A fake orgasm only leads him to believe that he's rocking your world when, in reality, he's no more skilled than a sloppy little puppy. Don't give him a treat if he doesn't perform the trick!
Assuming neither of you are deaf or dumb, you should be able to talk about sex: what works and what does not, what feels amazing and what tickles/hurts/feels like getting poked in the pooper. Honestly though, if you are partaking in this sort of intimate activity, you should be able to talk to one another.
Do you ever want an orgasm? Well, he won't just magically figure it out someday. If you keep faking, he'll have no idea that his current tactics aren't doing it for you. You don't even necessarily need to bring it up - just stop faking. He will definitely notice that something is amiss. You needn't say you were faking all along - the male ego is fragile, after all. Just kindly, perhaps steamily suggest what you want him to do. He'll likely appreciate the information.
Even if it isn't terribly serious between you two, teaching a guy what's what will make him a better lay for legions of lovers to come. Haha…come. You're doing him a huge favor in the long run and earning yourself some sweet, sweet orgasms in the process. If he can't take a grown-up discussion about sex, it may just be time to look for someone a little more mature. What's the point of getting him off if you never do?
Not sure what to have him do? He could watch you masturbate to get some ideas of how you like to be touched. Perhaps you could look at a quality sex book together. It's always fun to learn new skills! Be aware that some less-evolved men can be threatened by sex toys. It's just insecurity. Let him know that while a dildo or clit stimulator can be nice, there ain't nothing like the cock.
Just promise not to fake. Well, I'll allow the occasional I'm-tired-just-finish-already fakey, but try not to make a habit of it. It doesn't do either of you any good. When I was 18, I used to fool around with my boyfriend, then secretly masturbate after he'd fall asleep. A gal's gotta get off somehow! But we're not 18 anymore. Let's have the best sex we possibly can. Now is the time! Go forth and find those orgasms that leave you tingly, breathing like you just ran a marathon and quivering with a fresh dose of oxytocin.