I really abused my body at the end of my long drinking career, and it's took a time (1 1/2-2 years?) for the brain to clear and a lot of the memory to return. The tiredness lasted the first year, but I had "excused" myself and allowed a diet of sugar and caffeine in sobriety. Once I went to healthy eating and a little exercise, the tiredness improved. The 1st year was hard to fight through, but hang in there. If you can, nap when you're tired. Forgive your brain for now, as it gets tons better...just give it a little more time.
Congrats on six months!!!