Best position when losing virginity to reduce pain (especially having Vaginismus & Vulvodynia).
Hi, if you want to be most relaxed and take it at your own pace then I would maybe suggest being on top. This way, you can decide if you want to go further and see if movement is painful.
My other suggestion would be missionary with the bottom half of your body fully relaxed and to have the bottom of your back / your butt propped up on a pillow or two. That way, you can push away freely if anything is painful and it should alleviate any pressure down below.
Have lube on hand! It should help reduce any pain caused by friction.
You can try missionary position and use lube. But having vaginismus is very challenging for your sexual life even if it's not your first intercourse. It must be treated first if you want to experience sexual pleasure.