You won't get your blood glucose down on bread, porridge and weetabix. You could try telling the doctors it doesn't work, but unless they are diabetics themselves, they tend not to believe you.
There is no metabolic necessity for eating carbohydrates, so if you cut them down, your blood sugar should come down too. If you eat less of those foods you listed, you won't hurt your baby. He/she needs protein, good fats and viamins and minerals. So meat, fish, eggs cheese and vegetables, with a little fruit. Try it for a few days and see if it does the trick. Start with a breakfast of scrambled eggs. Test before and an hour after eating. then try a green salad, with low carb dressing and do the same. Try different foods and keep a record of what the effects are on your blood glucose. Show it to your care team. They will throw their hands up in horror and tell you "you must eat carbs!" You don't need them, but a little might be ok. remember gestational diabetes often leads to huge babies and early induction of labour. Keep a log of your food, your BG and tie it in to your baby's scans
Let us know how you get on and we all wish you and the baby a safe delivery in a few weeks time