Sex scenes
are very hard to write well - in theory it should be no different from writing anything else, and technically it isn't, but somehow... One problem is that the you've got twin pitfalls: ludicrous lush/euphemistic language on one side, and bald un-sexy details of plumbing on the other. The path between them is narrow - narrower than with other kinds of scene - but it is there. If your reader merely felt that they were a bit dry, and wasn't falling about with laughter or tossing the MS away in disgust you're doing pretty well already.
This book does just what it says on the tin, and is really helpful.
http://www.amazon.co.uk/Joy-Writing-Sex-Elizabeth-Benedict/dp/0285636421/ref=sr_1_1?ie=UTF8&s=books&qid=1220601761&sr=8-1
Things that help a lot include:
Make the most of whatever point-of-view and voice you're in. How would
that character think about it? What would they see and feel, what would they not mention or not notice? That way the reader experiences the sex (good, bad or indifferent) as the character does, and doesn't stand back and judge from afar, (which is when they might start giggling...)
Don't forget there's no need to write the whole damn scene from the first kiss to the last snore, any more than there is with anything else. Focus on the crucial moment of change (if there isn't one, you don't need the scene) and then fill in as much of the lead up to it, and lead out of it, as you need to make the change strong and convincing, and leave it at that.
There is a WW group - intimate moments - specifically for such writing. You might find help and inspiration there, too.
Emma
<Added>The other thing you have to do is completely forget that your parents might read it...