I'm exhausted after a few hours of being awake. I sleep 7+ hours per night, uninterrupted, no snoring, no apnea. Not dieting, no exercise, bmi=19.5?

Quality of sleep? How do you know if you don't have a sleep problem ? Need to consider sleep issue maybe not apnea but periodic leg movement and fragment sleep patterns exist as well also consider meds and if doing everything correctly need to have laboratory evaluation and a medical evaluation if the problem persist .
Doctor. Should consider getting a thorough exam from your doctor. There are many factors and ailments that can create and maintain fatigue- chronic fatigue syndrome, stress, etc. Need to start by providing a good history and evaluation.
Fatigue after sleep. Fatigue after sleeping all night suggest you are not getting restorative sleep. Make sure you have good sleeping patterns with no computer/tv one hour before, bed, exercise earlier in the day, no caffeine after 12, eat low glycemic foods, try sleepy time teas or calm's forte (if ovef 35, try melatonin), chelated magnesium can help; and also see your doctor.