I'm the same way. In theory, complex carbohydrates should be better as they take much longer to break down into glucose - where simple carbohydrates can be absorbed very quickly the shorter chain sugars they contain. But in reality, complex carbohydrates can be more of a problem for people with this condition, which is confusing for doctors. The exact cause of reactive hypoglycemia is still up for debate and as I said elsewhere, a lot of doctors still don't recognise hypoglycemia in non diabetics.
Now, it's true that complex carbohydrates take longer to break down into glucose and so don't cause the insulin spike (when eaten in moderation) that glucose itself would - therefor you should, in theory, find that when you've eaten a pizza and are feeling symptoms, your blood sugars aren't actually low. In other words, complex carbs don't cause a hypoglycemia (actual low blood sugar) reaction, as is repeated in almost any advice you find for hypoglycemia. Yet they do still cause symptoms in all those with this similar condition. Why, is a complete mystery to me and to the medical world it seems.
Some things important to bare in mind is that 1) everyones body is different, your symptoms will vary along with reaction time and what foods you can/can't tolerate. 2) If you have hypoglycemia, whether reactive or fasting, there will be an underlying cause. With reactive hypoglycemia, as I said, the cause can be very debatable and isn't very well understood. Some causes are thought to be hormone deficiencies, or a carbohydrate sensitivity/intolerance (which I have, and is the likely problem if you can't tolerate complex carbs/starches), or possibly an intolerance to certain starches/proteins. It could also be a temporary hypoglycemia caused by stomach surgery or pregnancy which are more straight forward explanations.
So as I said, I also have this problem with complex carbohydrates (bread, pizza, potatoes, rice, pasta, cereals, flour products, wholemeal or otherwise) and I'd love to get to the bottom of the cause. At the moment my problem is thought to be a carbohydrate sensitivity and so I'm diagnosed with hypoglycemia due to carb/sugar sensitivity. I can't eat carbs except for veggies in small amounts, and milk, milk is fine surprisingly as long as I don't drink a pint at a time.
My advice to you is to eat what you know you can tolerate, and avoid what you can't, because diet is a very personal thing there's no guidelines set in stone. Make a list, you know better than anyone what gives you symptoms and what doesn't. It sounds like, as with me, you need to cut out the flour, bread, pizza etc.
Secondly, don't over eat, just eat until you're comfortable, and eat regular. It's important that you don't over eat or this alone can cause symptoms.
Don't bank on an explanation, I've been searching for many years. These longer term symptoms are a mystery. Just adjust your diet to suit you, an explanation can come later.
Personally I'm leaning towards adrenal fatigue. This is just my theory so don't take it in stone. Adrenaline is one of the hormones produced to prevent a hypo in the event of blood sugars plummeting. When you eat simple sugars your blood sugar drops so far so fast, glycogen and other prevention hormones don't have a chance to kick in in time and so your blood sugar falls too low for a brief period (some people pass out for a few minutes for example). You should find that following a low blood sugar, your blood sugar will raise a little, about 1-2mmol, this is glycogen etc kicking in (unless the cause of your hypoglycemia is lack of these hypo prevention hormones of course).
With complex carbohydrates you don't have the spike, but you may still have a potential low blood sugar which is prevented by glycogen/adrenaline etc kicking in. In my theory, if you follow the wrong diet and are causing this reaction repetitively then your adrenal glands are going to get fatigued. Resulting in the symptoms like fatigue, brain fog, drunken feeling, but you won't find the low blood sugar.
In short, I think it's possible that reactive hypoglycemia, if not treated properly, can be accompanied by an adrenal fatigue which explains both the immediate and longer term symptoms you find with the condition.