I'm not sure where to post this. I figured here my be best. 

So over the past year, SO and I have been fighting continually and a lot of our problems are stemming from his mother. I've been seeing a therapist for 2 maybe 3 years now. Recently the therapist mentioned how MIL might be BPD and suggested I do some reading. Well one of the books I read was by Christine Lawson and my MIL is 100% a waif... but I got into the hermit section it is 100% me. I've never read something so fitting of myself. 

I told my SO about it and how I'm feeling and Essentially he told me he has known for about a year and read and hid a BPD book from me last year. And hasn't told me. 

My therapist has never mentioned it. We have talked about my controlling tendency due to childhood trauma, health anxiety, and general anxiety. 

Right now there is so much to take in but on top of that I feel betrayed by my SO, and let down by my therapist. Now that im reading up on it,, apparently it is common for mental health professionals not to tell patients this and it has me feeling like I've been let down or failed in some way because i feel like in the right circumstances, i could be a lot more receptive to it.. I'm not handling this well and I don't know if it is the news itself, the fact that I have been adamantly villifing my MIL for possibly having this and basically causing no end of torment/irrational/self inflicted problems towards me and SO. 

We have had a major fight this weekend and I feel like every bit of my feelings and behavior has been "dismissed" as a disorder rather than hearing that I'm having real feelings about things. I guess what is most upsetting is I place a lot of emphasis on telling the truth and being honest. I'm very against lying. And a situation came up where I'm saying he said XYZ and he said he did not. And I'm saying I remember. He is saying he remembers. It led into a major back and forth with him saying he didn't and he doesn't know why i say things like this. Because he wouldn't say that. Im saying he did so he is short tempered,, i'm crying then he leaves. 

Well later he comes back and shows me the portion on how this disorder effects memories and it's just absolutely upsetting. Because I know that a big thing with this disorder is lying, but I'm not! 
The article he is trying to reference is that because you're in a heighten emotional state, you don't remember things accurately. But I am having a hard time understanding how this can impact the cognitive abilities so much that it causes me to rewrite history and staunchly defend my history and not even know I'm doing it! I feel like if that is the case, then what else am I capable of unconsciously doing and completely rewrite it later? Or that if this is really a big thing with this disorder, why there is not more widespread treatment/info. This just seems positively mind blowing. And I'm not feeling well about it.