I'll keep this brief, though it's a twisty story: I was diagnosed with vaginismus about seven years ago. It was discovered not during sexual activity, but a pelvic exam. I only have pain with penetration. There's been various doctors and therapies, most of which were more confusing than helpful. The consensus seemed to be it was a "head" problem, not a "body" one and I could only get over it by developing a healthy attitude towards sex. At my most recent gyno visit, I was able to complete a pelvic exam/pap smear with the add of a sedative and my gyno noticed something interesting - even though I was not having the typical vaginismus muscle contractions, I was still in pain. Which is to say, the pain was causing the contractions, rather than the contractions causing the pain. So there's something else at play. The gyno guesses that it's the result of oversensitive nerves. Maybe.
Here's the thing - I could go my whole life without having someone stick something inside me. This doesn't impact my sex life as I'm asexual. I can more or less tolerate a pelvic exam with meds. Containing to try to get to the bottom of my pain problem will be expensive, frustrating and, well, painful. Is there really any reason I need to?