The blacking out symptom is what leads me away from panic attacks or generalized anxiety. Otherwise, from what I have read everyone has different symptoms for anxiety or panic attacks. What you are describing in your last comment does sound like a panic attack -- I wouldn't call it a "psychotic episode", because you aren't psychotic -- you are panicking! (Unless you do have psychotic issues as well, like Bi-Polar) As for anxiety: exhaustion, gastrointestinal problems, cloudy mind, as well as many other symptoms, can happen. Good luck on finding your answer and getting better!