I am just trying to think about how you were positioned in your family pachyderm. I was actually thinking today about what it means to be the middle child. I was with a lot of families today and I was thinking about you and paying attention to these children with you in mind actually. There was also three children in my family too, my brother being the middle child had a really hard time too. Although he either had Asperger's or compulsive ADHD because he was a challenging child, could not really sit still or pay attention for very long, tended to be in his own little world too, unfortunately he was constantly punished for it which only made his challenges even worse.
The reason why I asked you about the ages is, for example if there is only about a year and a half between the middle child and the youngest child, then the mother is tending to the youngest child when the middle child needs to have her listening and paying attention to him, it is where his mind is at. What tends to happen is that because the mother is so busy with the youngest, and the oldest child, if he has three years gain on the middle child, will have had more time from the mother, more nurturing during that crucial time in child development. The middle child will often miss out and get the kind of treatment you are describing, constantly being unheard and dismissed and told to stop whining. All the child is really doing is asking for nurturing, nurturing that all children need. But, if the mother is already on to the next child's needs (the youngest), she is more apt to be tired and short tempered and dismissive to the middle child's needs.
I am just trying to explain to you "why" you were punished and dismissed so much. I am trying to help you straighten this out in your subconscious mind that keeps triggering you to retreat as you do.
Pachyderm, the brain learns from anything repetitive, be it good or bad, the repetitive gets hardwired in our subconscious minds. When you say that you feel like you are going to get hit on the back of the head, that's real, that is a deep learned message in your brain pachyderm, that isn't your fault.
From what you are describing to me you get triggered, and your brain re-experiences all the emotional challenges, anxiety, and negative feelings you have from experiencing negative messages constantly from your mother when all you wanted was what "any" child wants, nurturing and attention.
I have these same challenges, a lot of them, if I get triggered bad enough I can really suffer for days. Well, I am very sorry because you have been trying to reach out for help for this, and because a therapist/psychiatrist is an authority figure to you, you really do feel that if you try to reach out and say what you need, that person will do the same thing your mother did to you. I think that is "sad" pachyderm. Your mother failed you because she didn't give you a chance to speak your mind, a child has to have that, it's so important. And it sure doesn't sound like she had the where with all to do it when you needed "again" at only 8, an important age, because she went through a divorce and ended up being a single mother.
Your brother's are not going to see it the same way you know, they most likely got more than you did, it probably was hard on all of you, but you got it the worst, when you deserved better.

OE