Hi there, brilliant advice above here and I'll try to avoid repetition.
I know a few young women with this problem. Some of them found that they got closer to success if they stopped trying to follow any idea of what female masturbation should look like. The archetype is the woman on her back providing direct stimulation to the clit, when this is just one variant on a whole spectrum of possibilities.
Those of us who are lucky grow up with an instictive method of pleasuring ourselves but a lot of women have to riddle it out and it can be like trying to crack a safe at times.
The Hite Report
I once read an incredibly helpful book called The Hite Report. It's a comprehensive study on female sexuality and the chapter that grabbed me was on female masturbation techniques. http://www.scribd.com/doc/10790993/Female-Masturbation-Techniques
This was the first time I had a read that other women, like myself, achieve orgasm more easily if they're lying on their front and pressuring the general area as opposed to going straight for the clit on their backs. It lists a million other ways, from women who have to squeeze their thighs together to ignoring the clitoris completely. I'm not expecting this to give you a fool proof method but I hope you find it as comforting as I did that everyone is unique and there's not a standard way. I think this helped me tremendously to stop thinking that I had 'failed' when climax didn't happen for me when trying techniques that I thought should make me orgasm.
Neural Pathways
Another useful article is Tracey Cox's blog entry for LoveHoney, adressed to a woman who had never climaxed with her partner and only orgasmed during solo masturbation when her legs were poker straight. Tracey runs through how we train our bodies and brains to follow certain routes to climax and it's possible to retrain them to find other paths....
http://www.lovehoney.co.uk/blog/2009/11/27/ask-tracey-cox-27-november/
Pressure and Tenderness
It's fantastic news that you are getting very aroused.. That can be the hardest part for other women. I too have a tendency to be over vigorous (usually when I'm trying a method that doesn't suit me) and look down below and it looks like someone's tried to vigorously rub me into non-existence with an eraser. If you feel you're going too hell for leather, you might find that lubes soften the blow. If not this, then perhaps putting a slight barrier between yourself and your hands could cushion the impact. This can be a God send to friction lovers who don't get off the slip and slide that lube provides. A number of women in Hite's report pleasure themselves by making a fist with the bedding, (scrunched up lingerie is more appealing) to grind into.This provides you with a stimulation over a wide area instead of using pin point precision on the clit.
Swollen
All this said, your labia swelling and changing colour is a natural reaction to arousal but discomfort, tenderness and irritation to the skin is not a good sign.
I suspect it could be this vigorous pressure that is causing you some numbness and ruining the party before you hit the jackpot. You might suit a stop-and-start method. Once you feel that you're losing sensation, change your method, decrease your speed or take a little breather. Many women also find that masturabting on their fronts allows them a greater control over the pace and strength of their strokes.
Giving Up (but not giving up if ya get me)
Also, don't be suprised if you're one of many women who find their partners eventually find the secret code before themselves. AdnaW has also written excellently on not putting too much stock in the big O but, perhaps, once you stop chasing it, it will turn up and suprise you. Psychology can be funny like that.
Partner Issues
It's a widely unreported issue that a lot of women feel that not 'performing' for their partners can make them feel as inadequate as a man experiencing similar dificulties. Try to reassure your partner that he is still blowing your mind. Orgasms are amazing but they are the 'end' of something and can be very brief. If he can get you half way there he is still doing something that requires good communication, intuition, talent and affection. Niether of you are robots and it's unfair to pressure either of yourselves to find a fail proof method.
You say everything feels better with him? Perhaps you're very, very close and in your case it takes two to tango. The solution may lie in your joint adventures, not solo masturbation. Could be a matter of time.
I know what you mean about jealously. I'm incredibly jealous of some men (and some women) who seem to be guaranteed a happy ending. It's shaped so much of how I think about sex and sexual politics. But always remind yourself that you are integral and at times crucial to the pleasure that gets him to climax. Men can orgasm from masturbation but I think most will vouch that it's a whole different game when you're really connecting with someone. It's this team work and a confidence that you're striving towards your orgasm together that might help you to climax whist having sex with him.
Kegels
One last thing. Have you tried kegel exercises? If you really work at them (and I don't mean a few clenches here and there) it could change your life.
I don't know if any of this is remotely useful or relevant but I hope it's provided a spring board for ideas. As long as you're happy, confident and getting pleasure from sex you've already got it sussed.
