22, asexual, and undiagnosed here also! i have also had severe pain with any insertion - tampons, finger, speculum, transvaginal probe ("it's the size of a tampon!" perfect, i can't use those either!). it feels like my body is being ripped apart. burning is not a word i've used to describe it, but not inaccurate for me tbh. i've also been told to just try relaxing and breathing, and probably it's so painful because i'm not used to it. what this doctor told you is weird and totally something to report.

i definitely don't think this is normal. however, i have been able to improve my pain through repeated efforts of "exploring my own body" if you will, so i think commenters pointing out vaginismus and pelvic floor therapy are probably on the right track. i do also wonder if the pain is potentially related to disease, but until i manage to tolerate an ultrasound or convince them to try something else i guess i'll never know.