I'm 30wks into my first pregnancy and am finding my energy levels all over the place. Some days I have lots of energy and others I have zero energy, even though my routine is pretty much the same... Something that I have found that tends to make me feel more energetic is drinking half a glass of water with a tablespoon of apple cider vinegar. I do this every morning. It tastes revolting, but on the days that I forget to do it, I end up feeling like crap by the early afternoon. I'm not sure how it works, but I heard somewhere that vinegar helps your body absorb nutrients better or something. So that, together with the usual stuff like keeping well hydrated and eating healthy seems to work for me.