Okay, NO. You didn't do this to yourself. You didn't know you couldn't digest carbs right, so there's no blaming yourself here, okay? Now you know, so now you can do something about it. And there's a whole lot of information coming at you right now, with a whole lot of numbers and whatnot... But especially at the start, try and keep it simple, because otherwise you're just going to feel trapped by this whole new lifestyle and way of eating, and if that's the case, if all the JOY of food is being sucked out of it, this isn't something you'll be able to keep up.
So... Forget cholesterol, calories and whatnot for a moment. (If anyone decides to give me a hard time for this, too bad. And yeah, I'd go for keto rather than a moderate LCHF because of the PCOS. If anyone wants to challenge me on that, fine, but it's HARD for a woman to hear she has to jump through hoops to get pregnant. Keto could help, where LCHF would be a slower process.) I'll keep it relatively simple, but if you want to know more, and when *you* feel you can handle more info, because you're getting an avelanche of it right now, and a lot of it slightly contradictory, do pick up Dr. Jason Fung's books. The Diabetes Code is a great place to start. The guy's a brilliant doctor.
But here's the basics: There are 3 macro nutrients: proteine, carbs and fats. If you take less of one, up the others. That way you don't become malnourished, still feel full, and keep from becoming vitamin and mineral deficient. As you can't process carbs (and thus, glucose) effectively anymore, you preferably up the fats. Yeah, fats. If you worry about cholesterol, 80% of it is actually made by our own bodies, 20% is what we eat. Once I started my diet I lowered my cholesterol, after it went up for a tiny little bit: If you lose weight, the stuff that's stored ends up in your bloodstream for a while on the way out, and you want it to leave your system... So don't worry if you go up a tiny bit for a while; it will pass. (I mean, i'm eating eggs and bacon every day. And my cholesterol is waaay better than it used to be, without statins!) So, back to diet. You're prediabetic, so you don't need to go as low carb as a T2 advisably would. BUT, taking into account you want to tackle your PCOS as well, I'd say, consider going keto. That means going so very low carb (less than 20 grams a day) that your body enters ketosis. That means it starts burning (body)fats rather than carbs for energy. If you don't want to go that far, try eating 50, 75 or 100 grams of carbs a day, which won't get you into ketosis, but will make your bloodsugars improve.
So, what foods should you avoid? Anything made with wheat/grain, so bread, chapati (I'm probably spelling that wrong, sorry), rice, peanuts, corn, pasta/noodles, potatoes, cereal/muesli, fruit, save for avocado, berries and tomatoes. Stuff that won't make you spike: eggs, meat, fish, poultry, cheese, butter, full fat greek yoghurt, cream, above-ground veggies and leafy greens, nuts, olives, extra dark chocolate, mushrooms etc. Dietdoctor.com has a whole lot of visual guides for foodtypes and what have you, so you really want to have a look around there. You don't have to become a paying member to have access to their nuggets of wisdom and meal ideas.
If you cut a lot of carbs in one go you could experience keto-flu, which really does feel like the flu... Muscles and joints get achey, headaches and such might occus, as your body purges itself from carbs and such. You want to up the salt intake while that happens, as you'll lose a lot of water weight (carbs hold on to water), and you might feel a little dehydrated. Bone broth and coconut milk could help with that, replenishing the electrolytes you lose. It could last anywhere from a few days to a week or two, but after that, you'll feel so much better. But it's all up to you. You decide what you do. Always keep that in mind. I'd advise a meter, so you can see what's happening with your bloodglucose (Testing before a meal and 2 hours after. If you go up more than 2.0 mmol/l, it was carbier than your body could handle). It'd help you decide what's right for you to do, how far to go, what works for you.
Take care of you!
Jo