How to treat vaginismus at home? Thank you in advance

I would recommend gradual desensitization: buy vaginal dilators - start with the smallest size and go to the next size as you become more comfortable. You should talk with your partner about this exercises, about your emotional condition and fears.
Collaborating with your partner and open communication can be crucial. You can try gradual penetration together (with dilators or without). You can agree on a non-verbal signal (gesture) that will inform your partner to withdraw from penetration (this is important because due to high stress, sometimes it's hard to name emotions or say something). I encourage using this gesture when you feel you can't endure more because of significant pain.

Please also read some scientific articles or publications from reputable institutions (avoid internet forums or social media as a source of knowledge). Many people find exercises previously prescribed by physiotherapists helpful. Many resources include Kegel muscle exercise sets, which can also be beneficial. It's important to rule out somatic causes of such discomfort (consult a gynecologist or sexologist).

Of course, often secondary problems are entrenched anxiety reactions, which can be modified using behavioral techniques (there are also books or articles available on coping with anxiety, mainly in the CBT approach).

However, I must emphasize that sometimes symptomatic intervention alone may be insufficient. This could involve psychological blocks that manifest at a less conscious level - in such cases, a combination of behavioral techniques with insight-oriented psychotherapy may be necessary.