(Sorry this is so long)
I feel like you say you feel where you had a slow leak and not recognizing the effects etc... This past summer I had a bit of a breakdown. I've been NC for 7 years and I honestly felt like I was totally fine. I have two younger sisters and I used to joke that I was the most adjusted of the three of us. But this summer right after my Spring semester was over, I broke down. I was crying and depressed and scared and angry. I was yelling at my kids and my boyfriend and I could tell that something big was up and I decided I needed to get to a therapist asap.
I searched for a long time for a therapist that would take my regular insurance (I have medicaid as well) and I couldn't find anyone, so I just called my county's mental health department. They did an intake appointment (walk-in style, no appointment necessary) and based on what I told the lady, diagnosed me with PTSD. She looked for a therapist in their office who would be best suited for my situation and also available ASAP. The only person they could get for me usually deals with addiction, which is not an issue I have, but she was available the next week and I couldn't waste any more time. I was falling apart.
I have been seeing this therapist about every couple weeks since summer. And we haven't really actually talked that much about Ndad and my childhood. Instead, she helps me process the things that are going on in my life currently. And for the most part... she lets me vent and then comments with some brilliant, often tiny remark that suddenly shifts my perspective and shuts down that part of me that wants to go round and round with all the ways I can't possibly fix whatever situation.
She has helped me see that self-blame is useless and incorrect. She has helped me see that my kids behavior is developmentally appropriate. She has helped me see that my story is relevant to all audiences, and because of that relevance, I should not feel ashamed of my story and I should not fear the response to it. She said to me last time that trauma isn't trauma because it was a particular level of bad. Trauma is trauma because of the way the individual experienced it.
We only get about 45 minutes of real time to talk. I took a huge chance just accepting this therapist based on availability. But this time, it paid off. She believes me and she listens to me and her insights are valuable, despite the fact that she is younger than me by maybe as much as a decade, does not specialize in childhood trauma and is super pretty (I thought I would feel uncomfortable talking about problems to someone who appears to have none... isn't that shitty? I was so wrong and stupid for thinking that...I hate admitting that).
My (non-N, amazing) mom says that she think that every single person on this earth should go to therapy, even if they feel fine. She thinks that we could all benefit from therapy greatly at one point or another in our lives. I think she is right. There is something really great about knowing that this person is paid to sit and listen to you and give you feedback. You can take it or leave it, but it is a relative stranger, giving their opinion in a way that can lead to broader understanding even if it is just understanding how one other person perceives your difficulties. That kind of ...just data is invaluable.
Having a therapist helps me stand on my own as much as it helps me stop leaning too heavily on my mom or sisters or friends or boyfriend. I can tell my therapist the stuff that my outside "network of support" has heard me beat to death already, or would be uncomfortable hearing, or I would be uncomfortable with sharing. Because she has an education in dealing with mental health, I can ask her pointed questions when I think of them, dealing with the why. We've discussed Kohlberg's model of morality and DBT (even though I don't have BPD) and empathy and dissociation and trauma and illness and what is reasonable and what is not reasonable.
In many ways, I am further along that some ACONs, simply because of how long I have been out of contact with my Ndad. There is a lot of stuff I've sorted through. I'm not angry with him anymore, I understand his disorder and I understand that it wasn't my fault and that he will never change. But the stuff that comes out now looks like this: I am angry with myself, I don't understand why I am not "fine", I feel like everything is my fault but react as though nothing is my fault, I worry that I will never change and I'm terrified that I am inadvertently damaging my kids in a way similar to how my Ndad damaged me, not because I am a narcissist but because I haven't had good parenting modeled for me and in times of high stress we automatically revert to what we know.
I highly recommend therapy. Especially if you are prone to higher level thinking about things, if you find a therapist with a degree, you can explore your mental health in a way that provides more concrete answers to some of the really confusing hard stuff. I always feel more stable when I have concrete answers.
Sorry this was so long.