There's a thread somewhere on here where people post what they think caused their diabetes.
Lots of different reasons, from genetics to steroids, to lifestyle, but a very common contributor is stress.
I'm not saying this to worry you - but to encourage you to take your stress seriously, and seek help sooner rather than later. Far better than struggling on and feeling overwhelmed.
How good is your diet? I ask because whenever I am stressed, the first thing to go is my efforts to eat well!
And your inability to concentrate? Well, that sounds like the classic 'brain fog' that kicks in when blood glucose is running too high. Perhaps reduce your carbs for a few days, replace them with more salad, veg, fish eggs and meats. If it makes a difference, you know you were eating too many carbs. If you still feel bad, then you've eliminated one likely cause and can carry on looking...
Hope this helps.