Withdrawal?

I might have to do some research but I am pretty sure I am experiencing withdrawal every time I finish a book. I have read five books in the past two weeks. Nothing special, just novels.  I find I get totally immersed in what I am reading for five or six hours at a time. The only reason I stop is because my butt is sore, my back is sore, my neck hurts or my eyes are sore. And then I feel exhausted and usually take a half-hour nap. I finished a book about an hour ago and found I was feeling let down. I knew the end of the story had to be coming, but still I was disappointed when I finished the book. So I took a nap. Now I have just taken the first shower in three days and realized I have to scoot out and get some groceries. When I get back time to have something to eat and maybe start a new book!