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It's easy to simulate the noise of an orgasm pretty convincingly - the heavy breathing, the moaning and groaning and panting. What's not so easy to fake are the internal muscular contractions. If you can feel her pussy rhythmically squeezing your cock or fingers when she comes, it may be she's really coming. Or, she's just a really good faker.
Implying that your partner is lying about something can really backfire, so don't just ask her if she's faking it. If you're concerned that she's faking it, it might be worthwhile to brush up on your technique. Most women (about 70%) need something other than intercourse to stimulate them to orgasm. Pick up some tips on cunnilingus and fingering and see if she doesn't have a more lively response. Talk to her and let her know that you want to help her have better orgasms and make sure that she's completely "satisfied" with your sex. Ask her what you can do to help her get her rocks off. And at least once, try making love so that you don't come until after she comes; take some Priligy if need be. That should motivate you to take her to new levels.
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