You're not crazy.
Are you able to identify specifically what you're so angry about? We can make assumptions, and I'm not being nosy, but an important aspect of therapy is being able to name your feelings and identify where they spring from.
Does the rage come from the loss of you mother and baby? Or do you feel your mum was let down? Or that you weren't properly supported?
Could you be angry with your mum for leaving you (anger isn't always rational)?
Anger can also be other feelings in disguise, like anxiety or fear. I've found that anger is an emotion which makes me feel powerful when I'm not, when I've had no control over the things happening. It can also be defensive, helping protect us from other feelings of desperate loss.
This page has a good description of the ways anger can serve to protect us:
https://griefdirectory.org/anger-in-grief/
I understand that calling it anger when you say rage may come across as minimising. Please know I'm not, I appreciate the intensity of what you've described, the overwhelming, sheer rage. One of the reasons I liked the above link was that it acknowledged intense rage.
From what you've said, I think the rage you feel is serving to protect you from being overwhelmed by grief, especially because you've said how difficult you find it to speak about.
I think you need to find a qualified therapist who's experienced in grief & trauma counselling. Someone who will help you feel safe enough to process these intense feeling in such a way that they won't swamp you, and won't pressure you to speak about anything until you're ready.
Can you stretch financially to paying for private therapy? NHS therapy are limited by number of sessions and i think you need to be working with someone long-term. From what you've said, and my own experiences with grief & trauma, it takes more time than the NHS allows for to get to a place where you can start to safely deal with the intensity of your feelings.
It might also be worth looking up complicated grief. X