It may be your subconscious holding you back. Can you fully say you trust your diaper to not leak at night, in any position, and even flooding the diaper from a full bladder? If no, then you need better diapers.
I used to have that problem too. Turns out it was the diaper I was using. It took a while after switching to betterdry/crinklz, but eventually I was able to get a full night's rest and wake up in a wet diaper. Part of the key is when you wake up, don't move or make any adjustments. Pee exactly as you are, then try to fall back asleep without moving too. Eventually your subconscious will get the message you don't have to move, and your diaper will keep you protected, so there's no need to wake up.