I was much like you in terms of lifestyle. Ate healthy for years prior to pregnancy (portion control, whole grains, low fat etc). Before and during pregnancy, I worked out. Strength training and cardio 5 days a week, until 36-37 weeks. At 38 weeks I’ve now stopped working out because it just wasn’t possible. You can imagine my frustration when I was diagnosed. Mind you, I failed the 1 hour by a large margin , and failed 3/4 values in the 3 hour test. The diabetes nurse went through my questionnaire answer and was at a loss on what to recommend because, in her words , “you already eat and workout like a diabetic”. Despite the healthy lifestyle, I failed by a large margin. Like one of the above commenters, I was one of the people who failed by a large margin but managed to stay diet and exercise controlled. I’m now 38+1 and due to my well controlled numbers, my OB decided I don’t need early induction and is willing to wait till my due date to go into labor on my own. This is nothing you did or could’ve done. It just happens and you can only do your best. Good luck with everything !!