Failing the 1 hour glucose does NOT mean you have gestational diabetes. The 3 hr glucose is a better determining factor. I have failed the 1 hour glucose in FOUR of my pregnancies but my 3 hr has always come back normal. With my last 3 hr it came back borderline high but still not diabetes, I was just told to watch my diet and sugar intake. Good luck and don't fret, wait until you get the results from the 3 hr.
My friend showed possible GD with her hour glucose test and went back to do another test, and everything turned out fine. She didn't have GD. You MAY have it, but you may not have it. Just like the tests for down syndrome, just because it shows positive doesn't mean 100% your baby has down syndrome, my aunt had positives with both of her kids for DS and they were both fine. Tests can be wrong, don't stress about it, take it one day at a time and if you do have it your doctor will be able to help you out and I'm sure everything will be fine.