OBs office scheduling issues

So I'm 26 weeks tomorrow and I just found out they couldn't fit me into their schedule to test for gestational diabetes until I'm 30 weeks! I had GD with my last and it was uncontrollable and led to my son being born at 37 weeks. I'm so frustrated and nervous with this. This is the absolute soonest they can fit me in, I had to fight to get it done before 32 weeks. I had them schedule my future appointments too to avoid this scheduling issue again, and they only scheduled me one appointment per month! With my last I was seen twice a month until it became weekly the last 2 months so I'm feeling like my and my child's wellbeing is being neglected because they've clearly taken on too many patients. Idk what to do. I'm eating the best I can to limit the GD issues but that doesn't mean I can go without monitoring the closer to delivery I get. I'm just stressed. I hope they schedule me more when I fail the glucose test. And yes when I fail, even my OB doesn't expect me to pass with all my risk factors and big baby.