Borderline Personality Disorder is the new black these days.
No therapist has any business opining that someone may have BPD unless that therapist has evaluated the person. BPD is very difficult to diagnose -- you don't do it secondhand.
And your therapist is wrong. BPD is not all about thoughts. It is all about emotions. The emotions always come first. Then the thoughts. Then the actions. BPD is about emotion disregulation.
And yes, there are successful treatments for BPD. The include Dialectical Behavioral Therapy, Schema Therapy, and Mentalization Based therapy. Many people with BPD get better.
I also recommend reading "When Hope is not Enough" by Bon Dobbs and visiting his website www.anythingtostopthepain.com. He can give you tools to save your marriage.
But that's not what you want to hear. You want a pass to leave your spouse, and I'll leave everyone else on DCUM to give it to you. No mental illness is more stigmatized or more misunderstood than BPD. So grab yourself a copy of Randi Kreger's Stop Walking on Eggshells, a couple cookies and a nice cup of tea. That book will have you filing for divorce before you can finish it. And since it so terribly written, that may be half the reason.