I am always tired too. It's so hard right after lunch until when I go home.
The little bean (or two) growing inside you is sucking up all your strength, so sleep, sleep and sleep again, while you can. I've heard from both my sis and SIL about those long sleepless nights for a few months after the little ones are born. :)
What a great pic! Those little babies are are going to zap your energy for awhile! That's a good sign that they are growing nicely. (I like referring to them as twins hehe). The 2nd tri should be great though! :-)