Failed Glucose Test!??!

Hi I'm a FTM just barely in my third trimester, 28w1d and I failed my glucose test, it was a test that I fasted for 3 hours then got my blood drawn and I failed. We are doing another test on Friday where I fast and then we draw my blood 4 times and I sit there in for the 4 hours or something like that. If I fail that second test does that mean I have diabetes? And if I do what do I do from there? Is it just a change in diet, is it testing my blood sugar every so often? I'm just at a loss of what it all means :/ any advice / info is appreciated (: