Sugar feels low but isn’t!!!??

I’ve been monitoring my sugar. Even when it’s at normal level I feel hungry, very tired, weak, etc. crave sugar like crazy. Tried changing my diet. Cut out most sugar, unless it’s extremely low. Only drink water. Dr not sure what’s wrong. Just that I’m pre diabetic but that it wouldn’t cause these symptoms. I’ve also been diagnosed with sleep apnea. I’m 28. 135 pounds.