Welcome to the forum, you certainly have a lot to contend with. If you are on steroids for your other conditions they can trigger diabetes.
It is not uncommon to receive poor support from your surgery and people find by learning abot the condition it becomes clearer how to manage your blood glucose levels.
The learning zone here is a useful resource with some links but also you might find this link helpful with some do's and don'ts and some ideas for modifying meals.
https://lowcarbfreshwell.co.uk/
If you need to lose weight then doing that will help with lowering blood glucose as will reducing carbohydrates in your diet.
Metformin will only help alongside dietary changes.
How much you need to do depends on what your HbA1C is, but there is no need to go hungry by basing meals on meat, fish, eggs, cheese, dairy, vegetables and fruits like berries whilst reducing or cutting out things like potatoes, rice, pasta, bread, breakfast cereals as well as the more obvious cakes, biscuits, sugary drinks including fruit juice.
Protein and healthy fats are fine but all carbohydrates need to be had with caution.
Some people think they should cut out carbs but you can still have some but limit them, the suggested amount is less than 130g per day.
There are other approaches people use, shakes based, calorie controlled but it is only you how can decide what approach you will find enjoyable and sustainable.