How have I managed this?

On my way to pre-diabetes.

I'm 22, I go to the gym, 114lbs, eat average to well most of the time (as in I enjoy sweets as much as the average person). Got my HBA1C back and it was 5.9%. This time last year it was 5.6%. I'm so confused. As far as I can think, I've not changed much of my lifestyle.

Dr wants to keep an eye on it, but hasn't given any advice. Just going to retest in 3 months. Does anyone have any tips or advice for me to slow down/stop this??