Anybody else?

I’m 34wks pregnant and get very sudden spells of INTENSE dizziness like I feel as if I’m going to pass out and I lose my balance if this occurs while standing and have to sit down, followed by shortness of breath, blurred vision, ringing ears and becoming very lethargic. I took my blood pressure after my most recent episode and it was 116/75 which is almost perfect. I called my doctor after hours but they haven’t called back yet. Just curious is anyone else experienced this and knows what it is? Could it be related to low iron. They started having me take a supplement supplement at my last appointment which was on Thursday. Sorry for the babbling just concerned!