Sorry to hear your in hospital, it's a bit of a wake up call, you know what needs to be done but it's feeling confident to do the right thing and get the right support. I hope that your current situation brings you to the attention of a good nurse and you will start to feel supported. (We're here too if you need any advice !)
I might sound like your diabetic mum here so hope there's some useful advice I can offer, try and start a diary now going forward, write down: Time your reading was done, your BG levels and insulin taken, this will help you manage your doses better and can tell your team how you are doing, if you dont have a diary (i'm sure the hospital can get you one) then use a jotter pad. Recording your results identifies trends and patterns (i.e. taking too much or not enough insulin) also gives you more control over managing your levels better. As suggested it's best to try and eat a low carb diet - so leave out bread/pastries/rice/potato/desserts these cause your levels to rise quickly, try and eat more green veg, salads, more meat, fish and eggs, low fat cheeses - so as an example I would have a curry but without the rice, for breakfast I make a muffin with flaxeed meal and eat cheese, or bacon and eggs or an omelette with courgettes and feta cheese, that sort of thing, the less quick acting insulin I take the less margin for error with going high or low = better control, it also means I can see what my background is doing too.
Your don't have to gain weight with insulin, just do regular exercise and eat well, please make your priority to get better first. You can have a good life with diabetes but you need to embrace it and take control of it, as time goes on developing good control get's easier but speak up and make sure you are getting support.
PM me if you need any info/advice, i've done DAFNE and follow Dr Bernstein's advice, I have a daughter so am determined to live a healthy life, I don't try to dictate to others as we are all individuals but if I can offer support then happy to help - big hug x