Sounds like you are very busy working! If you are feeling more tired then usual maybe you should see about reducing your work hours a little. I've been experiencing light period pains with Braxton Hicks Contractions on and off since about 28 weeks. I'm now 37w 4d and my bub is still cooking It can sometimes be a sign of labour, or in your case, preterm-labour. So just make sure that you and your midwife are both in tune with what you are experiencing... There is lots of preparation going on so it is normal to experience different sensations of course! Good Luck with everything!