I have had such a hard time losing weight, or even maintaining a constant weight wince I've been diabetic. I find that it mostly has to do with the consistency of my blood glucose though, in my case.
As far as having to eat a certain amount of carbs - are you carb-counting, or taking injections on a sliding scale. Because if you do carb-counting (which you can still do if you're not on a pump), you can eat whatever you would like, but just take insulin based on how many carbs you eat. You can even compensate for exercise in that case. Have you actually spoken to your doctor/nutritionist about wanting to lose weight?
I know that one of the nurses I see at the clinic is always telling me that it's just a matter of exercising and not necessarily trying to lose weight, but simply looking fit - which never really addresses my concerns, especially since it was my doctor who was telling me to lose a little weight, but my nutritionist at one point was willing to give me some information and tips to lose some weight. It definitely does seem harder though because of having to worry about insulin and the effects of the insulin on your body and everything.
Just know you're not alone! Good luck with everything and be healthy! =)