Ms Arielle, I don't know if you are still reading this but I think this is caused more by the OMAD than CAD. Some people can do OMAD but apparently that is too big a meal for you. If you were doing CAD with 2 CM and 1 RM you are still eating your carbs only at one meal, but you meals are smaller.

I am diabetic. I never get sleepy after breakfast or lunch because they are small low carb meals. Dinner tends to be a larger meal and if it contains any carbs, it puts me to sleep easily.