Hi and welcome to the Chiari forum.
Yes, you can have Chiari symptoms with a 3mm herniation....many Drs will not acknowledge that unless it is 5mm's or more, BUT it is the obstruction of CSF flow that is more important to review then how long there herniation is...even more the width of herniation is more important than length, as a wider stubby herniation can cork up the area and not allow the CSF to flow.
In addition to Chiari it is possible to have a related condition....Ehlers-Danlos and even POTS sound like a possibility for you.
I have been diagnosed for many of the same things as you....premature ovarian failure....leg numbness, blurred vision, Hashimoto's thyroiditis.
Educate yourself on ALL related conditions to Chiari and then research Drs....as you want a true Chiari specialist....not just a neurosurgeon willing to do surgery....finding the right Dr is key!!!
And remember you are not alone.