Hi Nikki! You are exactly 1 week ahead of me!

You fasting BSL's are mean't to be under 5.5 so yours seems okay at 5.4. It's hard to know though as it's also your blood sugar levels during the day and after meals that are important. Try not to stress too much about it. Just go and have your GTT and see what happens. Usually GD manifests between 26 and 30 weeks, but I guess it's not impossible to get it later on.
If you do have it and your bubba is large for gestational age they may want to induce you acouple of weeks early. Did you measure bigger than normal with any of your other pregnancies?
Good luck with your GTT and let us know how you go.