Normal or cause for concern?

I'm 29 weeks and for the past week or so I've been experiencing some strange symptoms. Sometimes when I lie down (on side, not back) I get that blood rushing to my head feeling (you know like when you're upside down for a few moments and your head throbs). I also keep waking up in the night with similar, or feeling dizzy. And some nights I wake up so short of breath I feel like I can't breathe at all. Ive always had heart palpitations but I seem to be getting them more often lately too. Is this normal?! has anyone else experienced this? I had my 28 week check last week and blood pressure was fine then, bloods came back low in iron but everything else ok.