I have been extremely tired with this pregnancy. I don't remember being so tired with my daughter, but a lot has changed in eleven years. Have you had any problems with your thyroid. I had to have my medicine increased since I have been pregnant. I am pretty sure it needs to be increase again. It is so hard to tell whether it is pregnancy or thyroid. Plus, I have been sick with this one a lot!
Maybe you could ask your doctor to check your iron at your next appointment. Anemia could cause you to feel extra tired and worn out. But the interrupted sleep probably isn't helping either...plus you're almost in your third trimester, where things seem to require more effort anyway. But I would have your doctor check to see if you're anemic. It's pretty common in pregnancy, and if you are, a simple iron supplement (I use an over-the-counter one) will help.
:-)