Passed three hour glucose test then developed GD later?

Has anyone passed the three hour glucose tolerance test and still developed gestational diabetes? I failed the one hour test and passed the three hour test, but my baby has been measuring really big (nearly 5 pounds at 32 weeks). I’ve asked my doctors about the possibility that I actually do have GD and no one seems particularly concerned except one told me I could just follow a low carb diet to be extra safe... at my doctor they don’t test my urine at regular appointments so they wouldn’t find GD that way. Anyone have a similar experience or find out they do have GD passing the test?