Eating sugar

I am still relativity new to diabetes. I have had gestational diabetes twice. It then came back when my baby was 2 months old (Sept 2012). I made sure that I was sticking to the rules given to me by the dietitian at the hospital, but then I read on here about carbs and decided to follow a low carb diet instead. I also introduced a hormone balancing supplement to see if that would help. My sugars have dropped from high teens to 6-7 2 hrs after eating and around 4.6-5 fasting. I am down to 6 units with breakfast and 8 with dinner.

On Sunday I was at my mother in laws and ate something very naughty, that I know I should not have. I reluctantly tested my BG 2 hours later to find that they were 6.2. I was expecting them to have shot up as I had consumed 2 sugary desserts

Can anyone shed any light on this? Is it normal to be able to handle sugar and not carbs??

Thanks Viv!
There seems to be so much more to diabetes than I originally thought and it seems to effect everyone very differently.
I've had to drop down to 4 units with breakfast now and 6 with dinner as I had hypos within 2 hours of eating yesterday. So strange. I expect it will shoot up again now my insulin units are decreasing! :?