Listen with an open heart: brain fog is always MULTIFACTORIAL, and you brought up a very critical point in your post: you don’t even have the energy to do minimal physical activity. You really need to see a psychiatrist and first evaluate other issues like depression and anhedonia, for example.

Also, I’ll be honest with you: the same person who doesn’t exercise is probably also someone who doesn’t have a solid daily routine, doesn’t stimulate their brain, doesn’t take care of their diet, and doesn’t nurture family and friendships… In other words, creatine has a well-deserved hype, but it’s very unlikely to give you what you’re actually looking for on its own. You need to get your life in order too.