I posted this on the other thread, but I might as well post it here, too.
You inability to have sex can be caused by a few things.
1. Abnormally thick hymen- The hymen (thin tissue that protects your vagina, and why bleeding occurs during the first penetration), has any different shapes and sizes...and they all look different. Sometimes, the hymen is abnormally thick. This can cause painful intercourse and the unwillingness to have sex. A gynecologist can surgercially break the hymen for you to fix the problem.
2. Vaginismus- it is a psycological disorder that causes the fear of penetration. It will take time to get by it, therapy may help, but you just have to trust your husband.
Go to a gynecologist. They can tell you whether it is psycological or physical.
This is a very interesting situation . . . I wonder how you both arrived at this point? Was it do to religion or some other outside factor? If nothing else, I would try to have "closeness sessions" where you explore each others body, giving massages, kissing, and so on, not being in a hurry. Hopefully, you would both work up to hand stimulation and oral stimulation, and then eventually once you both are excited, it would carry you on to trying an intercourse position. Keep the performance aspects out of it and don't expect that it would work the first times it is tried. Rather than "having sex", just enjoy relaxing and being close.
Once you prepare yourself to bear some pain, thereafter you will wait ot sence that pain and also will do experiments from several ways, angles etc.
I remember reading about this years ago. It's evidently really common and lots of women experience it. It's quite easily resolved evidently.
Unfortunately I don't know much about it, so hopefully someone can help you. Personally with something like this, although it's not a life threatening thing or anything, it is something I personally would see a doctor about, because there are things that can get rid of the problem. But I think it was therapy or something similar, so a professional would fix you up in no time, but someone like me on a forum would have no chance.
Hope that helps somewhat. Good luck, I'm sure a doctor could help you with that in no time.