Hi Amy, welcome!
Sometimes when our blood sugar dips low we feel tired and draggy. This might happen sometime after eating. If a person is diabetic, I believe the feeling might be more enhanced than in someone who has a normal metabolism. I don't know if that's what's going on with you but it might be an explanation. Best of luck with the tests. One way that you might fight against that tired feeling after waking up from a nap is to cut down on carbs in the meal if you're eating a lot of them. (And the carbs would raise your blood sugar which isn't a good thing. After it rises, then it would crash and that's the tired feeling you might have.) Let us know how it turns out.