When you say your blood sugar results were high, what sort of numbers were you getting?
It sounds quite Type 1 like to me, but at this stage I wouldn't even worry about what type it's called - if you are losing weight at that speed, you are thirsty at that level, and your vision is going, you need to get treatment now, not in four weeks. GPs are used to seeing Type 2s, because the vast majority of diabetics are Type 2. They can therefore sometimes not realise that they need to move a bit faster when they encounter someone with other types of diabetes.
Go back to the doc and say you need urgent help - or take yourself to A&E, if the doctor won't refer you faster.
In the meantime, try and avoid eating carbohydratey foods and sugary drinks, and make sure you keep drinking water. For the moment, I wouldn't worry too much about the high fat/low fat thing. That's quite possibly important in the longer term, but you need to get your blood sugar down now!