this isnt a abnormal thing though
Just because it happens every few weeks doesn't make it abnormal. Your body needs to sleep and refresh itself, and you're only putting off an inevitable "crash" when you hit the wall with this. A doc can prescribe something to help you establish a better sleep pattern. I really would go see your doc as soon as possible. Getting a second wind is one thing, but you don't get a second life if something happens when you "crash".