Reddit reviews The Hite Report: A National Study of Female Sexuality

I hope you don’t mind me proposing an alternate hypothesis.¹ You didn’t mention your age or range of experience, but it seems to me you might just have had a lot of crummy sex. The stereotypical inexperienced sexual encounter is making out followed by plain PIV² until the man orgasms. For most men, that’s a satisfying, if not exceptional, encounter. For many women, that’s duller than a dental cleaning, disappointing, sexually frustrating, and sometimes physically painful. Most of my women friends’ first few sexual relationships fell squarely into this category.³

In my view, that explains everything you said: Lousy sex would, obviously, explain your distaste for partnered sex. Feeling put on to do things you don’t want to do would make almost anyone feel viscerally repulsed; at least that’s been my experience. And, as your dating relationships progress, I assume your partners have only gotten more persistent, until your disgust overpowers your warm fuzzy feelings. Is it possible that’s what’s going on?

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1. I’m going to follow the other commenter’s lead and refer to your sister as “you.”
   
   
2. Penis-in-vagina sexual intercourse.
   
   
3. You might enjoy reading The Hite Report on Female Sexuality (Amazon trade paperback; pirated PDF). It’s a representative sample of women’s differing views, experiences, feelings, and opinions on their sex lives, given in their own words. It’s old, but not outdated, and more in-depth than even the wonderful discussions in sexxit.

Standard disclaimers: Orgasm need not be the goal or end-state of sex; just a pleasant effect sometimes. Per the Hite Report and more-recent studies, around 70% of women won't achieve orgasm through penetration alone. Add to that that most partners are going to be different in some significant way or other (in size, angles, neural pathway/sensitivity, stamina, etc), and you're not gonna find a catch-all solution. That said:

1. Plain ol' missionary. Well, missionary with a slight bolster/wedge under her hips. Depending on your builds, this allows for your pelvis and lower abs to stimulate the clitoris through pressure while you're deep inside. Also allows decent access to the breasts, neck, and ears (good supplemental stimulation areas, for most.) You can lean back slightly with her legs around your waist, or lean forward with her legs over your shoulders to experiment with different angles and see what seems to work best for her and when. Great for 'dialing in' what does it for her. If you have an upward bend, great for g-spot stimulation. Lots of options for control of penetration depth. You're in control of a lot of factors, so great for lasting quite a while if you're doing your kegels and in tune with your orgasm cues.
   
   
2. Girl on top. I especially like this on a sofa where I can sit up. She's in control of stimulation, so it's a great opportunity to see what does it for her if she's not shy. Also: Breasts in your face, and her posterior is perfectly positioned for rubbing and/or other things if you're feeling adventurous. Hard for endurance, for me, since many girls tend to get wildest when I'm needing them to be still to edge off. May be rough on her knees, potential hazard to your shaft if everyone's too excited.
   
   
3. Lazy doggystyle. Like standard, but have her move her legs inside yours, and both lean forward until she's lying on her stomach or over a pillow with you still inside. Great for girls who aren't comfortable with your full length; you get a nice tight squeeze, she gets to not feel impaled, everyone wins.
   
   
4. Freestanding/against a wall. Because it's raw, powerful, and impressive as hell.
   
   Hope some of that was helpful.

On every other sentence: http://www.amazon.com/The-Hite-Report-National-Sexuality/dp/1583225692