hey, i'm not sure that vaginal orgasms are actually very common, but i think that kegel exercises practiced consistently can help in many ways by developing the muscles, control, blood flow and focus of that area. Use the muscles during sex and stimulation.
Practicing energy work during sex could help too. Try to focus on the sexual energy in the pelvis, that you and your partner share, and imagine creating more and filling the reproductive organs and uterus with this energy. If you can feel the energy and/or visualize it then you could try to phsyically expel the energy with your muscles. after sex, imagine the energy circulating from your genitals up to your crown, and then down back and around again. This disperses the sexual energy through out your body so it doesn't stagnate.
Trying out breathing techniques could really help you there. Do research on sexual breathing techniques, and also just experiment with your breath during stimulation, and see how it changes your responses.
Getting near to clitoral orgasm while having sex, then letting up on the clitoral stimulation before you cum, and still continuing to have penetration might work.
Trying out techniques for squirting might help develop the awareness of muscle movement.
You can always just stimulate the clitoris and have an orgasm that way, while having sex, which is what you've probably been doing.
These are just ideas, and it seems like a lot of work for sex to me, but you could try the techniques out alone, and one at a time with your partner. I've never been too concerned about where my orgasms cum from, but it is rare that i have an orgasm that feels mostly vaginal, and it is a really intense feeling.
I think the key is to stay relaxed, ha ha ha.
Now we need someone to bring up the best positions that do the trick without the clit...