This is way more common than people think. That mental fog happens because alcohol disrupts your sleep architecture - you might sleep for hours but never get proper REM sleep. Plus it dehydrates your brain tissue and throws off neurotransmitter balance. Some people are more sensitive to it than others. I used to get it bad until I started taking B vitamins and magnesium before bed after drinking. Also found that sticking to clear liquors helps. There's a detailed breakdown at https://unitedrecoveryproject.com/rehab-blog/brain-fog-after-drinking/ about the actual brain chemistry involved. Staying hydrated during and after makes a huge difference too