The only things I can think of here is maybe a cluster of 3 things together.
Physically wise brain fog is almost always candida (when doctors and naturopaths find nothing else going on). And trust me naturopaths and docs seldom spot candida either.
Then the fainting sounds like they could be rooted in panic attacks. Your "subconscious" knows or fears that something is going on. Fainting is common with panic attacks.
The the chocolate sounds maybe like a slight allergy, maybe in relation to your body being run down and maybe just temporary or something. Maybe a panic thing too.