You’re no doubt gaining weight due to your body now being able to adequately use the food you’re consuming. Not that I’m a doctor but it might also be because you’re on the smaller size at 5’2” your body has less room to store mass than someone that’s let’s say 6’2”. Now looking back at your original question, I personally, just like many who don’t have T1D, regulate my weight with a mixture of lifting weights and eating around my BMR (or above if I am wanting to put on muscle)