Hello, and I hope I can help you today. There can be a number of reasons why a woman cannot achieve vaginal penetration, some physical and some psychological. However, if you have never had an examination by a gynecologist, it would be in your best interest to make sure your vagina and hymen are anatomically and physically normal first before investigating other causes. Some women can be born with a membrane at the opening or inside the vagina that can make both penetration and normal menstruation possible. Menstrual blood can get trapped inside you or be pushed back into your pelvis through your fallopian tubes, causing pain. So your concerns about your hymen being the cause of the problem are certainly valid. Given your pelvic and back pain issues, I sincerely believe you will benefot from an examination and consultation by a gynecologist, preferably an experienced one who also performs gynecologic surgery as if you do have a vaginal septum or imperforate hymen (the medical names for the condition you may have) it can be corrected with surgery. I hope I was able to adequately answer your questons today and that my advice was helpful. Best wishes, Dr. Brown