I can help you today.
If your wife isn't comfortable talking about it then I would tend to think that maybe something did happen to her as a child or that she was brought up in a home where sex was a taboo or sex was dirty, or that sex is all men want or some other ridiculous notion. I would suggest that she first speak to her MD to rule out any organic problem such as hormone levels which may contribute to her lack of desire. Then I would suggest she meet with a therapist who can help her explore her feelings. She may be suffering from depression or any number of other disorders that are affecting her thought processes. I am going offline for awhile so please comment on my posting and I'll get back to you when I am back online.
According to her, she likes sex, (in my opinion just traditional, missionary) and that I want it to much.
Hi, If she purports to like sex but not nearly as much as you, and has no interest in exploring then I think that if she gets the okay from her doctor, hormones okay, not depressed then you may benefit from seeing a couples therapist who specialized in sex related issues. Again, if she likes sex but can do without it she is saying something about herself and possibly even your relationship. If she says she can't explain it then she needs help exploring the issue.
not much else you can do, it is how she currently feels about the subject and herself.
There is no way you can explore her childhood experiences without professional help.
If she even wants to go there, which is doubtful.