Hi - yes, one of the problems is that there is a lot of contradictory and confusing information about carbs on the internet. Some of it seems to be almost deliberately misleading and difficult to work out.
In brief - by definition, anyone with Type 2 diabetes has a problem dealing with sugars. That includes not only sucrose but also fructose (in fruit) and lactose (in milk) and other carbohydrates. If we eat them a lot of the sugar ends up not being used for muscle fuel but gets converted to fat or just hangs around in the blood.
So you didn't have the same thing to eat, as you added a banana, and the additional (and considerable) sugar from that banana probably bumped up your blood glucose. So, a learning experience.
I don't eat bread, pasta, rice, most fruit, potatoes, beer, most root vegetables, or sugar.
I do eat meat, fish, dairy (double cream, cheeses, etc) green veg, some berries, and some pulses and legumes (I am not too bad with these but many people report unaccptable BG rises, so be careful), onions and tomatos.
I aim for around 20g carbs/day - equivalent of around one apple. You don't have to do what I or anyone else does, and what I'd recommend is continuing what you're doing, working out what's best for you. Learn from the results and make the changes that help you.