I've been feeling the same way, I'm a nurse in a critical care unit and work night shift so keeping my energy up has been near impossible! I found that I got dizzy and light headed very easily, of course preggo brain made me forget to mention that at my last appt with my midwife, so I tracked down one of our OBs at work and she told me to start taking 325mg of iron daily with my prenatals. It has made a huge difference, I still get short of breath pretty easily but the constant light headedness and dizziness has definitely subsided. Hope that helps! Oh and you can find the iron pills at just about any grocery store...but make sure you keep eating plenty of fiber because it definitely is constipating
Im 18 wks and have been feeling a bit more dizzy but just more so with sudden movements, if it persist without or is cause of concern I would speak to your OB/MD :)