Exhausted in 3rd trem

Rachel
Anybody else exhausted? I mean can't manage anything more than a snail's pace? I get weekends off and today hoovered one room with breaks to get breath back and cooked tea. On between I gave slept and just slowly walked up the stairs for a bath and shattered again. Baby is measuring small too. Am worried something us wrong as this is my 3rd and not suffered with this before.