Fun isn't it?! Diabetes under control, wedge suddenly out of control! If your diabetes hasn't been tightly controlled then you probably will find that you put weight on easily as your sugars come down. A stone in a week does seen like a lot though. I'd try cutting your calorie intake and making sure that you're getting the right kind of calories. I tend to stick to 1200-1500 calories a day. That keeps me full and maintains my weight.
Hope you manage to find the right balance soon!
Good luck
Em x