@kyles101 you absolutely do NOT have yourself to blame (and it's taken me two pregnancies to come to terms with that). GD has nothing at all to do with what you have done or eaten, it's 100% down to your placenta and hormones. You can't cause it!
I've had two very different experiences with it - first was fully diet controlled with very little diet change and no need for meds. This time I'm on overnight insulin. Neither are my fault, it's just my body and the way it handles insulin. Plus, getting older.
Shout if you have any questions - the website and Facebook group that I've recommended before are my absolute saving grace. The advice is different to the NHS guidance, but it does explain the research behind it.