Ok...I have this problem too. When I ask the doctors they seem perplexed, like I'm crazy. I can't find anything on it. Let's chat in private...
There are no nerves in the back two-thirds of the vagina, so don't let that worry you. Maybe as far as the "mind thing" part of the issue, you could talk to a therapist (not a sexologist) about any anxieties you have that might block you having sexual enjoyment.