my OB just rescheduled my glucose screening

My OB just rescheduled my glucose screening??? I had problems with my blood sugar and a strong family history of diabetes prior to pregnancy (and my doctor knows this). I've been checking my sugar and it seems to get high sometimes but my OB said it was perfectly normal. They had originally scheduled my screening at 28 week 2 days and now it's scheduled exactly on 29 weeks. Is it just me or it absolutely ridiculous that they're waiting this long when I have a family history or diabetes and problems with my blood sugar usually?