Hi there
I'm going through a similar thing at the moment and have just enrolled in some study.
I'm not a SAHM, I work 3 days a week, but I have been doing this job for almost 5 years now, know it inside out and don't really have to think about it, so I need something to keep my mind going.
I think it's a mixture of both the sleep deprevation and also a little "use it or lose it".
Is there a way you can do a little further study to get your mind ticking over?
Sorry I can't be of much more help but I can definitely relate!