I immediately thought depression as well. I've had bouts with it and it ain't no fun... Also have had similar confusion issues and chalked it up to my mind being subconsciously preoccupied (not that i was thinking of other things while trying to pick out yogurt but that I couldn't give my whole concentration to picking yogurt). This is a little dark, but I've had two suicidal friends who took antidepressants to correct a chemical imbalance, once they felt better they stopped taking them and felt worse than ever. I think they were SSRI's. Your diet may be causing some sort of imbalance or deficiency. Anyway, if you do go to the Dr. and he/she does prescribe an SSRI or other anti-depressant, you will want to do A LOT of research and read testimonials/forums from people who have had experience with it before trusting your doc and filling the script. Hopefully it is some sort of easily fixed mineral deficiency. Have you tried taking a break? Like a 5 day or so break from all exercise with your favorite unhealthy meal included? It may be a step back from your diet/weight loss plan but it would be a very small price to pay for you to feel 100% again.