Hi there - As someone diagnosed with prediabetes, it's a sign you could be o your way to diabetes (most likely Type 2), but on the other hand some folks can stay pre-diabetic for years.
That isn't trying to dissuade you from trying to improve your health, just trying to get across that I would urge you not to panic.
In terms of what prediabetes is and how it works, in most cases our bodies make enough insulin (which helps regulate our blood sugars), but our bodies don't handle it that well, meaning some of it is effectively "wasted", but along the way our blood sugars rise a bit because our bodies aren't being as efficient as they need to be.
You highlight that you are carrying some excess weight - which is very common in folks with pre-diabetes and diabetes (as well as lots of other factors), so it would be helpful to trim some of that back, if possible.. How do you find Victoza? Has it helped you trim at all, or does in more impact your appetite? It can be a very clever drug, but different folks find it impacts them in very different ways. Have you been offered any alternatives to Victoza? Although there are a number of similar medications around these days, they all seem to be in short supply from time to time.
To be honest, whilst the standard suggestions for those with prediabetes/Type 2 diabetes is a cut down on sugars and other carbohydrates, such as bread, potatoes and rice (just naming the most common of those), your situation is complicated by your very long-standing eating disorder. Are you currently getting any help with that? If you are, are they aware of your challenges getting a hold of Victoza?
To be honest, I would feel uncomfortable going too much further in terms of dietary suggestions without knowing where you might be with treatment for your eating disorder. It would clearly be very important not to do anything that would cause issues with your treatments or potential outcomes.
Please don't think I'm trying to be unhelpful, or unwilling to try to help, I'm just concerned the help you need in the first instance might be with specialist professionals, rather than well-meaning folks on the internet.