@Maygirl - welcome to the forum. I just read a lovely phrase this morning - "very gradually, your body's
need for glucose creeps up beyond what the blood system was meant to deal with - this is insulin resistance".
Pre-diabetes is a terrible name really, because it sounds inevitable that diabetes will follow - it needn't. Your body is just producing more and more insulin to deal with the amount of blood glucose. Why that happens is like a "too much of a good thing" issue, like if you had too much coffee, or exercise; you need more to have the same effect. But - it's a very slow process, nothing is going to happen fast.
It's bound to feel like a big, scary thing - but many many people are on this trajectory - then at one threshold you are told "pre-diabetes" and at a higher level you are diagnosed.
The good news is that small changes now can have big effects, and get you off that trajectory. What you do will be up to you, but many here find that simple changes, like reducing starchy vegetables, (starch turns to sugar quickly) or sugary fruit juices have a big impact.
Good luck with your appointment.