Hi and welcome.
I suspect lack of suitable dietary advice is your problem, but you have come to the right place for that.
Firstly it is all carbohydrates which affect your BG levels,not just sugar and sweet stuff,so you need to ration bread potatoes, pasta, rice and particularly many breakfast cereals, including otherwise healthy foods like porridge and fruit (in all it's forms including dried, fresh and juiced). The game changer for me was realising that if I was going to eat a lot less carbs, I needed to eat something else to provide me with energy (calories) Most NHS advice is low fat, low sugar and moderate wholemeal/brown carbs, but increasing your fat intake will make a huge difference to your diet if you cut the carbs. Fat provides slow release energy, it doesn't spike your BG levels and because it takes longer to digest it keeps you feeling full, so you are not tempted to snack between meals and in fact you may find that just 2 meals a day are enough as oppose to carbohydrates which hit the blood stream in a couple of hours and then leave you feeling hungry and wanting to eat more. Since I cut my carbs right down (I no longer eat bread or pasta or rice and just a very small portion of porridge oats or potatoes every once in a while) and eat more fat, I eat so much less and I don't feel hungry. There is a growing wave of scientific thought that the low fat advice we have been following for the past 50+ years was based on flawed and possibly also cherry picked data and may in part be the reason why we are now experiencing a diabetes epidemic, because food manufacturers found that carbs were a cheaper substitute for fat, so low fat products are pretty well always higher in carbs.... even the likes of milk.... take the cream out and skimmed milk is higher in carbs because the cream doesn't contain carbs and you can sell the cream separately so increased profit. Similarly low fat yoghurts contain more sugar and starch than full fat yoghurt because yoghurt is watery and tastes naff once you make it with skimmed milk. Many of us have coffee made with double cream with our breakfast of creamy Greek Natural yoghurt with a few berries (which are the lowest carb fruits) and seeds and chopped nuts or an omelette or a fry up. (no bread or toast though) It is hard to feel deprived when you start your day with a coffee made with cream and a fry up, so thi all makes this low carb way of eating sustainable. It is important to increase your activity levels too and a brisk daily walk is the ideal choice.
If you would like to tell us what you currently eat and drink for an average breakfast, lunch and dinner we can make low carb suggestions which should help you head in the right direction but using your BG meter to test before each meal and then 2 hours after will enable you to tailor your diet to your own body's tolerance of specific carbs, which can vary quite dramatically from one person to the next. You are looking for an increase of less than 3mmols after the meal for the carb content to be OK.
Would just like to add that I was a sugar addict and heavy bread and potato consumer pre diagnosis. A year and 4 months down the line I just don't miss them. I may have a small portion of potatoes or sweet potato once a week but I don't eat bread at all. I have experimented with beans and pulses but find that they also spike my levels badly, so tend to avoid those, but I eat lots of eggs and meat and cheese and fish and nuts and mushrooms and salad with creamy/cheese coleslaw and leafy green veg cooked in butter or cream cheese and lots of cauliflower cheese made with obscene amounts of cream cheese and grated cheese. Interestingly, despite my diet now being high in fat and particularly saturated fats, I am not putting on weight (I am a normal BMI) and my cholesterol which was not overly high to start with, has been reducing slightly without medication.
Anyway, apologies for my "war and peace" of a post. Hope you find some of it helpful. Definitely continue to test frequently but use a system of testing before and 2 hours after food so that you get maximum information from the results and use that info to guide you.