Dear Charlotte,
Don't let your weight be the reason why you don't take insulin. Running hyper (high) will cause you more issues then you really want to have. Maybe not right today but in the long term the harm is quite serious both to your body and to your brain. You deserve a happy life and part of that involves getting to grips with your diabetes.
Having said that there is a way to keep it in check. I have had type 1 for 32yrs or so and have never had trouble keeping weight off (I actually would love to put it on!). What you need to do is set up some regular gym time, watch the carbs you eat and avoid stress as much as humanly possible (I know that's a tricky one).
What I have done with the diet might help so I'll share.
1. I avoid bread like the plague.
2. I don't eat rice, requires stupid amounts of insulin
3. I only have potatoes and/or pasta at lunchtime so that my biggest carb intake happens early in the day when I will be active for the rest of the afternoon and burn it out.
4. I don't drink alcohol, its effects on brain and body are just not worth it in my opinion. If you do keep it to a min and avoid beer at all costs (it's estrogenic and will make you put on fat faster than you can imagine).
5. Avoid cereals in the morning, they are mainly just sugar loaded flakes (at best). A good portion of eggs, bacon and/or sausages works just fine gives you the protein and fats your body needs to get going.
The idea is to have fats/carbs early in the day when I'll be using them and having a protein (and relatively carb free) meal in the evening. You could try something similar but adapted to your own needs and see how that helps.
The next thing to do is exercise; gym is the key don't only do CV exercise you need to do some weight training (not as much as us chaps do though) but a little regularly. Combine the two, it will help the muscles consume the glucose out of the blood without needing extra insulin to do so. Research has shown that the two combined have the best effect on our HbA1c results.
The whole point of that is to keep your insulin at a manageable level as low as possible for you to feel good and have good readings. Don't avoid it because of weight issue please don't, the complications are not worth it especially not when you can get in good shape even when you are on insulin! (just think of bodybuilders who abuse the stuff to get fit! if it's good for them then it's good for us too
I hope that helps, if you need to feel free to ask for more info. But please PLEASE don't skip your insulins...
Best wishes!
Frankie