It sounds like a Vasovagal syncope, which is one of the most common causes of fainting. Vasovagal syncope occurs when your body overreacts to certain triggers, such as the sight of blood or extreme emotional distress, or dilating for the first time.
The vasovagal syncope trigger causes a sudden drop in your heart rate and blood pressure. That leads to reduced blood flow to your brain, which results in a brief loss of consciousness.
I would recommend not dilating unless lying down. I also think that you should give our center a call, Maze Women’s Health, to further discuss vaginismus, diagnosis and treatment options.