Vaginismus is a painful condition considered a sexual dysfunction and a pelvic floor muscle dysfunction. The muscles at the entrance of the vagina involuntarily snap shut when penetration is attempted, making it painful or even impossible. Many with vaginismus describe attempts at sexual penetration as "hitting a wall." There's much more information about what causes vaginismus and how to treat it (as well as links to treatment tools and online support groups) over here. Physical therapy is usually needed (be it at home or with a physical therapist), and mental therapy is needed for some. The condition is vastly under-researched.
For me/us, at it's absolute worst, vaginismus made anything trying to be put into our vagina feel like a flaming knife. It was excruciating both physically and mentally. We were diagnosed with vaginismus at age 18 and we were not able to have pleasurable, pain-free penis-in-vagina sex or insertion of toys/fingers/anything until age 25. We are now in our early 30s, and we occasionally still need to use dilators for at-home physical therapy exercises, but sex is enjoyable the vast majority of the time and if the muscles spasm, I'd call it discomfort, not as bad as it used to be.
We've also since found out that it seems to be present for some alters more than others. This actually makes a lot of sense, since vaginismus is said to be caused by a fear of penetration (be it due to previous abuse, medical trauma, religious shame, being convinced that sex will hurt the first time, or- to the frustration of many with vaginismus- the dread of experiencing vaginismus pain itself can keep vaginismus going when no other fear caused it in the first place). There was a time we didn't know why our vaginismus was happening (or that we were we). We now know that some of us were very understandably traumatized and afraid.
To be very honest, having to deal with vaginismus when many doctors and gynecologists seemed to not know what it was or even debated online if it was real and professional treatment was too expensive for me to obtain for a long time had a pretty big impact on how I/we approach dissociative identity disorder when mental health professionals often don't know how to treat it and debate online if it's real and professional treatment is too expensive for me to obtain. Not my first rodeo, but still a real bitch of a situation, honestly. And I'd like to say: it's time for those in healthcare, mental or physical (as well as people in general) to take these effects of rape and childhood sexual abuse seriously instead of further isolating people, denying treatment, and making their lives even more difficult because you don't want to believe their suffering is real. Get the fuck over your own discomfort and disbelief so you can help your patients! Discuss why treatment should be more accessible and affordable! Educate yourself and your peers, and learn who to send your patents to if you can't treat the condition yourself! Doing this will prevent suicides.