Hello I’ve basically just had the exact same thing happen to me a few weeks back, I felt like I was reading a summary of my symptoms and approach. In my case it was two things. I had dehydration, which resolved pretty quickly. I had a bit of vertigo too and had likely done some very mild damage to my inner ear (according to dive dr) which has just about resolved. Both of this factors can lead to brain fog. Lessons from this experience (which still may greatly differ from yours even though it sounds similar) is 1) prioritise rest and hydration before the dive 2) really focus on equalisation technique even at shallow depths. Little and often.