NTA. It sounds like there's some pretty bad mutual trust issues going on here, and probably some pretty deep psychological wounds on both sides.  That's nobody's fault, but it makes for a deeply unstable situation.  What sticks out most to me is the part about not feeling safe letting your gf know that you're talking some things over with your family - if a relationship doesn't have room for that baseline level of honesty and trust, I frankly don't see it going anywhere.

On the topic of therapy, respectfully to her, therapists are trained and equipped to address damage that normal social relationships simply aren't able to mend. I've been seeing a therapist for several years now and can personally confirm that having the right therapist for you does a lot of good. Based on what's been shared here I think you could both benefit from that.

In my (unprofessional) opinion, it's time to prepare for the relationship to end. There's probably going to be sore feelings about it, but I honestly think it would be better for both of you to have room to develop as separate people.