Dan,
Your profile shows you are a T1 and haven't been diagnosed for very long. Like most of us you may have lost weight before diagnosis. It takes time to put it back on and if your blood glucose levels are still on the high side then you may still be losing weight.
Yes we have to watch what we eat and take the right amount of insulin for it, but that doesn't mean we have to eat too few calories and lose weight.
The previous posters are correct that we need more info to help ,
My questions would be about your glucose levels , what do mean by watching what you eat and what type (s) of insulin are you using.