I use to have that, I had to take sleeping pills. I took a full packet (about 20 tablets, 1/day) and after that I've always been sleepy (from when I wake up till when I go bed) but I can't sleep E.G. why I'm up at 5AM.
EDIT: Just felt like throwing this in, sometimes I'm so sleepy I can't tell the difference between people (E.G. I start calling my dog mum and talking to it) it's fucking freaky. Only for a minute/two then I snap out of it, happened today like 2 hours ago. I started sending commands to some random guy on MSN instead of my msn bot. It's not because I don't understand it's them (E.G. I know my dog is my dog) it's just that for some reason my brain thinks my dog can get me a drink for like 2-3 seconds if I haven slept in like 20 hours >.<