I don't have any memories of my childhood, maybe 12 downwards, normal?!

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Sigmund Freud characterized memory and consciousness rather well. His idea is widely contested, and even he modified it later on, but it is still in use, and provides an accurate picture of how memories work.

You have your unconscious, you subconscious, and your conscious. I'm assuming you are familiar with these terms. You unconscious is a large group of memories heaped together, in the lowest levels of your brain, past quick remembrance. You cannot summon them at will. There is a hallway which all your unconscious memories are squeezing into, attempting to enter your conscious. The hallway is your subconscious, and your memories are all fighting for a way in, along with everything else that may be there (your pet dog's fur texture, your favorite subject in primary school, your ex's phone number, and that useless formula you crammed for your physics test in high school). At the end of the hallway is a room. That room represents your conscious. Anything in there can be picked up by your conscious if you happen to pick it up. It can be seen as a roving light that may stumble across that memory if it is lucky. At the door, however, is a security guard, who will reject all memories that will cause embarrassment, shame, or elicit any negative emotion.
So there you have it. It was later modified, as Freud saw this as how the mind worked, originally. He later ditched this analogy, and gave us the superego (conscience), ego (rational mind), and id (base desires) which operate in both unconscious and conscious. However, the above analogy, he claimed, is still an accurate representation of how memory works, even if it doesn't show how decisions are made.

i am the same no memories from since i was 10... but i think it from diabetes

Dude me too! I can't remember anything from before maybe 10 or 11? Only fleeting things but I don't know if those are real or just realistic dreams from back then etc.
I have been told that my father used to drink a lot back then too, although he managed to hold down a full time job etc, and I've been told that my mother and father fought a lot back then before they got divorced. And coming to think of it my memories start when they divorced and we moved to England. Interesting. Maybe the same for you?
I've always wondered that maybe my brain has repressed some serious **** from back then but it can't repress like 10/11 years can it?
I was thinking about maybe getting hypnosis or something as I heard that works but on the other hand they can also be 'fake' memories if that makes sense.
Or maybe regression therapy?
Couple of thoughts there for you.