Firstly - deep breaths!
It does not mean you are too fat! Some people who get GD are very thin, with low BMIs. I was overweight, with a high BMI, and I didn't get GD, even though I have the family history & am the wrong side of 40.
Did your midwife tell you to attend a special clinic (I'm guessing you never spoke to her, but did she give you an appointment, or just ask you to phone next week?)
The bulimia is worrying. The problem with it (among other dangers), is that it will be impossible for you to get accurate blood sugar readings, and, planning a healthy diet will also be difficult.
Have you admitted to your midwife that you have bulimia? If not you must. It is really important, especially in light of the diabetes, that your obstetric team know this. They cannot treat you properly, without full & open admission.
I know it's hard, I suffered from bulimia for 25 years, and have made myself vomit recently.
The best you can do over the weekend is to google low GI foods, and try to eat based on those. Don't binge on chocolates/biscuits etc, and try not to vomit. Put your hand in freezing water, or suck on ice, anything to take your mind off it.
The diabetes has been discovered - which is good news, so please don't panic about that.
Gestational diabetes does have a risk of stillbirth, if uncontrolled, so for your baby's sake, please stop the bulimia, as it will be much harder to control if you don't stop it. xx