I agree with TeenyT... I was absolutely exhausted last pregnancy and felt like I was in a 'fog' constantly - looking back, I really don't know how I continued working, but I just thought it was 'normal' pregnancy fatigue. When it didn't let up after 13 weeks, then 16, I wondered if my iron was low as I used to be vegetarian and was still not a big meat eater. The hospital refused to test my blood levels, so I went back to my GP, by the time I got the results, I was 22 weeks. My iron levels were a little low, so my GP put me on iron supplements and I had continued taking elevit the whole pregnancy for the iron. I had 4 weeks of energy, but then was back to the same.
Now, they only found out my real problem because I lost my baby at 37 weeks and then they tested for EVERYTHING! Turns out that my thyroid (TSH) levels were too high... and were again when I fell pregnant this time, so I am now on thyroid medication. Trust me, this pregnancy tiredness I am feeling this time is NOTHING on what I felt last time, so I know that last time was really abnormal. It is really worth checking too as low thyroid levels can lead to mental impairment in the baby. Don't want to scare you, but I was a bit p*$$ed off when I found out as it could have affected Lexie and the hospital wouldn't test me when I asked. It is hard when you have nothing to compare it to though. Good luck!