Gestational diabetes

ND • Ttc
One hour test with non fasting was 171. Normal range was less than 140 so doctor suggested a 3 hour test which I completed yesterday. Got a call early this morning that I have gestational diabetes and need to see a nutritionist and diabetes specialist. I'm 29, in the normal weight range. I eat healthy. I'm also a vegetarian. Where did I go wrong? I'm so devastated! Seems like I let everyone down, especially my baby who was counting on me.