Eating terrible and gestational diabetes?

I am 13 weeks and 4 days pregnant. I have been eating terrible most of my pregnancy. I struggled with nausea/vomiting my entire first trimester and the only thing that appealed to me was junk food. I’ve never ate so much take out in my life. I’m worried about the gestational diabetes test. Now that I feel better is there still time to change my habits and improve my chances of not having gestational diabetes?