Rose,
Sorry to hear that the GD has been hard for you to control. I can't comment on the insulin but I understand the constant watching what you eat and monitoring your blood sugar levels is a PITA. I keep telling myself that it is all for the good of me and bubs. I have 2 and a bit wks til my due date and I tell you I can't wait until I go back to 'normal'. The last few weeks have been getting harder to eat properly......... (Don't want to put you off). I go back to the GD clinic on Friday, so hopefully they will 'push' me out for another fortnight and then I will have my baby by then (here's hoping anyway).
With your diet are you 'grazing/snacking' rather than having big main meals? This helped me to control the sugar levels better.