this started happening to me around 24 weeks as well. i didnt even have to be doing anything and all of a sudden i would get hot flushes and go really dizzy and sometimes my vision blacked out or a felt nauseous. unfortunately it lasted for weeks. i had numerous blood tests to check iron levels and BP test but they were all fine. my m/w just put it down to rapidly elevating blood/sugar levels and says its completely normal in pregnancies. basically she said to eat numerous small, healthy meals a day and when you go from laying down to standing up do it in stages i.e stop for a bit when you get to a sitting position. also from personal experience try not to go out alone if you can help it. i had a dizzy spell while standing in kmart and my vision blacked out and i fell over, i was just happy that DP was there and a lady at the checkout muct have seen it coming coz i recon she was standing over me before i hit the floor. it was very embarrassing lol

take care of yourself hunni