Nuvigil - helpful but needs time?

I had brain cancer in 2009 and now have simple partial seizures due to the treatment. Ive been taking Nuvigil to help with my anti-seizure med fatigue for most of this time, but I'm questioning if my body reactions to it are normal and im starting to wonder if im just addicted to it. Here is how it works: I set an alarm to wake me up at 7:00 am to take the pill, then go back to sleep. I generally wake up again around 9, but I have to lie in bed for at least another hour. If I get up before then, Ill feel fine for maybe a half hour/hour and then all of a sudden all of my energy just drains away and im horribly exhausted for the rest of the entire day. It just seems so odd. It needs over three hours to fully work and makes me feel worse if I dont give it that time? If I don't take it at all, I feel totally different, more like a foggy sleepy zombie than complete exhaustion. Does anyone else go through this? I take 1/2 of a 150mg tablet. Any more gives me heart palpitations. Im on Lamictal 300 mg xr