Life after 9:00 PM??

All I want to do is sleep these days... I mean, that's pretty much all I've wanted to do since I graduated from college, but since getting pregnant it has become an all-consuming desire! I can't even stay up past 9 o'clock most nights. Take yesterday, for example. It was Saturday. I slept in until around 8 o'clock (which is actually kind of late for me), and had a nice, not-overly-strenuous day. I got some work done for school, and the three of us (me, Gus, and Florian) went to go see "Zodiac." I should have been able to stay up until 10 or 11 o'clock without any problems... but, once again, I was in bed by 8:30 and asleep by 9. I'm like an old woman! From what I've read, though, this is extremely common in the first trimester. I just feel constantly fatigued. It's really bad when I'm at work, and I start fantasizing about taking naps. sigh...