Hi,
I've had this too, went to gp last week as I feel like i'm going to pass out all the time and very lacking in energy. Just walking up the stairs I feel dizzy!! As well as having the vomiting virus thats going round, she said my bp was low. Got checked for anaemia and glucose levels, they came back normal. She thinks I should cut back my hours at work (I work shifts, some 12 hours, some 9 and some don't finish til 10.30pm - way past my usual bedtime!!), am back in work today after being signed off for the last week so going to talk to my boss about it but my boss is rarely in a good mood so not sure how she'll take it!! If she's not very receptive, i'll have to speak to HR or occupational health cause I can't cope with long shifts at all.
GP said low bp could last for whole of second tri and isn't that uncommon. Just hope it improves soon - not nice feeling like this all the time!