Laveila - whilst I can't speak for yourself and your friend I will say this about my story:
I always had pain during penetration and my OH is (just above) average in girth. I was a virgin when we started so didn't know what sex was like and we were long distance. I never used insertables due to the pain and couldn't insert more than one finger (still can't). I thought the pain was normal and with plenty of lube and time - it was manageable and once he was inside and I was settled, 8 times out of 10 the pain would settle down and we could enjoy the sex.
It was only once my body started responding to the anticipation of this pain I always had (as Gyrator mentioned) and my body started tensing that the pain increased such that sex was impossible 90% of the time and only possible with a tight condom to pull him in the rest of the time that I was pushed to see a doctor. I was examined and other than a slight redness to the skin I was healthy. But my GP, being a wonderful lady who believed me when I said the pain came before the psychological response and this was not in my mind, referred me to a gynae. Several tests and treatments later we still had no idea what was causing my physical pain and a year or two later my gynae got bored - decided it was in my head and referred me to a therapist (what a failure that was).
6-8 months after that, I was diagnosed with the connective tissue disorder which affects not only my joints but my skin, gut, muscles and nerves. I didn't put two and two together until I went to the GUM clinic to get a little lump checked out and mentioned the unresolved problems and the fact that I had a diagnosed connective tissue disorder. The lady at the GUM clinic advised I went back to a gynae with this new information as this was likely the cause of the pain and a gynae could now help me manage it better with the full picture. Finally, I know the cause (albeit an unexpected one and whilst I've had my condition all my life - it was only when it rapidly deteriorated that I realised that daily pain *wasn't* normal and got diagnosed).
People go for decades with my condition never knowing that the pain they have isn't normal because it never worsens enough for them to get it checked out and get diagnosed.
So what I'm trying to say is - I only know why I have pain during sex for a whole load of chances. 1) My joints worsening and being diagnosed 2) my GUM lady knowing that connective tissue disorders can affect the skin and 3) me actually happening to mention those things in the appt! I could have gone decades never knowing.
The pain could be for a whole host of reasons, but it is possible that there *is* a cause - you just don't know it yet. Maybe your skin is particular sensitive or extra elastic - nothing negative, just a minor alteration in your own make up that means you have pain/discomfort during sex.
Wow, this is a bit of an essay. But hopefully it's relevant? It sounds like you've tried all the things I suggest in my blog post here but maybe you'd find it interesting to read? http://damoreable.blogspot.com/2011/07/vestibulodynia.html
Gyrator thanks for the kind words. I'm going through a bad patch lately - as I said, penetrative sex less than half a dozen times in 2011 (but we make up for it plenty in other ways :P) but I have an appt with the gynae in August so hopefully that combined with the new info of my condition will help us get a good balance and at least make sex possible again!
Adx
If you've read to the end - well done :D
Oh - also - edit to say, I'm wonky - tilt back too far and am diagnal inside so maybe that plays a role. The OH has to enter at an angle.