Executive functioning is the new key word to describe some of the ADHD symptoms. This is a really good link that explains part of that.
Medication wise it sounds like you just have not found either the right dose or the right med. Instant release meds (compared to extended release) tend to hit harder. Of course, the advantage is that they are out of your system sooner so can be taken on more of an as needed basis.
You do need to let your doc know what is going on. It might be worth trying a lower dose. In fact, a good high protein breakfast always helps and will also lengthen the effective time of the med.
Are you on an instant release or XR?
Also, any chance the meds are interfering with your sleep? The exhaustion should not be happening.