So I figured I would share my experiences with this. I stumbled upon this forum a few months back wondering if I was the only girl who had to get her kicks from humping.
I started probably back when I was 12 and I'm 19 now. I started by mounting and rocking a rolled up sleeping bag and settled on finding the best control while one the corner of a clothes hamper, the plastic square ones. And I used a tee shirt or something to put on the side to cushion as I rubbed up against it.
I was ashamed of this for years, and every time I tried to orgasm by direct stimulation using fingers or even with boyfriends I could never get the same response from my body. And I wasn't about to tell past boyfriends of mine "hey, sorry, you're not going to make me orgasm no matter how hard you try because I only reach it by humping things".
But recently I've found a few compromises that I figure are worth sharing. A determined and creative boy I'm currently dating helped me find a way to reach the same orgasm as humping but without having to physically and embarrassingly mount objects.
One thing I found that works pretty well is sitting cowgirl style and rocking back and forth while he's inside of me, this gives him pleasure and imitates the motions I make while masturbating. I will warn you though, it's a bit hard to get comfortable enough on top in order to make the fast motions necessary to finish. But it gives, at least my body, the similar shock waves that I look for.
The second and most eye opening thing I've discovered involves just turning that humping sort of masturbation into not only a successful finger, direct stimulation alternative, but also gives my boyfriend a way to rub me and make me orgasm even longer and better than my old humping tactics used to. Amazing, let me tell you.
It involves simply letting him rub your clitoris while you let your body do what it knows to do best to have an orgasm; move. I lay on my back, because that gives him easy access, and while he moves slower to faster down there I move my hips in small by fast humping motions. My muscles almost do it naturally now. Speed up and slow down your thrusting motions and get fast and into it as you start to feel that familiar humping orgasm coming on. Maybe you'll surprise yourself your body knows what it likes, so give it to it. It is yet to fail for me since I discovered it. And it rocks my world to know that there's a way for my boyfriend to finally give me an orgasm before or after I give him oral, so it's sort of a fair trade. Rock the hips up and down, and you have to really want it. Focus all of your mind on that feeling, I can't emphasize that enough.
Hopefully this helps someone out there. I had it in my head that up until a few weeks ago there was no physical way for me to have an orgasm without humping objects directly. But I've been proven wrong.
Don't give up, and don't be afraid to experiment to find what you like! Good Luck!