Hi and welcome
I have had type 1 diabetes and been through two pregnancies (in 2009 and 2010/2011) so know what you are going through and can hopefully help a little. I don't know about gestational diabetes but since you are on insulin then I'm guessing it's pretty similar! I went on a DAFNE course at the start of 2009 which really changed my life for me esp for my control. I pretty much eat what I want although I am on slimming world so it's within their boundaries. With regards to sweet things ( I also have a sweet tooth! and during pregnancy 1 I craved pick and mix sweets) and other things - the diabetes doesn't restrict me, and that's because of DAFNE. With insulin you really aren't restricted. I will dig out some of my DAFNE stuff and scan it in for you. Basically it works on a ratio system, so, for me personally, for every 10g of carbs, I inject 1 unit of my quick acting insulin. There is a whole DAFNE book which give you details and you can look on the packets but as you go along you get familiar with it anyway. I work on a 2 1/2 : 1 ratio for all meals and 1:1 for snacks. For breakfast, I'll have 10-40g carbs so 2.5-10 units of quick acting insulin. Obviously i needed to work out with my diabetes nurse what worked for me. Testing regularly is important and although it sounds complicated it really isn't when you get the hang of it!
With my pregnancies; both pregnancies I was at the diabetic clinic every 1-2 weeks in hospital and got extra scans which was nice

. Pregnancy 1, I was in hospital from 33 weeks being monitored as I had polyhydramnious (excessive amniotic fluid) and they were worried about cord prolapse. My waters broke at 35+5 and I had my daughter by "emergency" c-section. She was totally fine and weighed 8lb 8oz (despite having hBA1c's of 5-6% throughout my pregnancy!). Pregnancy 2, I was again in hospital from 35 weeks for the same reasons and because my insulin requirements had started dropping, had daughter no.2 by planned c-sec at 36+1, she weighed 9lb 9oz (again with excellent control!!), had no probs. I now have two healthy, happy and raucous girls aged 3 and half and 2 (well in 3 weeks) yr olds!
Have you been told anything about what they think about delivery? Not sure where you are in UK but when I was pregnant, I was one of the first members in a support group for diabetic (type 1/2/gestational) mums and mums to be in Leicestershire who support each other with diabetes & have regular meet ups for cake/coffee/walks/kids play dates etc. It's been going strong for about 4 yrs now. There may be something local to you like that or I can give you the details for this one as there is a facebook group.
I never buy "diabetic" products - they are a total waste of money as there is no reason why you can't eat "normal" foods by adjusting insulin. Make sure you drink no/low sugar drinks too - Robinsons R juice is sugar free or diet things like coke/lemonade etc, sweeteners in tea/coffee. Fruit juice needs insulin as it's got sugar in - I use that for hypos

Not sure what the weather is like over there right now but here in Denmark it's baking hot and that always makes my blood sugars low but great excuse for lollies/ice cream hehe.
PLEASE do not feel desperate/useless/helpless - bombard your diabetic team with questions and concerns and always feel free to message with anything even if it's just to moan!! :-D
p.s. Sorry for the essay!
Caroline x