I have the sense that this feeling comes from how new this is, along with a few deep-seated insecurities that my newfound vulnerability has pushed to the fore.
Sounds like this might be it. I have been having issues with insecurities myself recently - and yeah, I feel vulnerable.
A modern day polyamorous polygamist My Online Journal
Me, center of a MFM V-shaped polycule (38F)
Wife to DarkKnight (40M) & PunkRockAwesomesauce (42)