Im in the exact same situation right now, tbh i think the brain fog is one of the worst sides you can have.
Feel your pain brother..
dude, i thought i had brain fog to until i realized i was just thinking about finasteride too much. I also think the brain fog occurs in the adjusting phase, if at 2-2.5 months your still feeling it then maybe its not adjusting and a real side but my brain fog significantly went down since when i started, im spry and witty again while still on the same dose.