Dizzy @27+ weeks with twin pregnancy

I’m expecting twins and am just over 27 weeks and tonight I’ve been dizzy for 4 hours straight. I have eaten and drank lots of water today however I may have over did how much I did. I just attended an event with my husband where I sat most of it but wore my maternity compression panty hose as I have awful varicose veins that throb so bad especially across my shin. I cannot seem to get the dizzy to go away... I took my sugar text last week and haven’t heard anything so I’m assuming all is well and I’ve always had low blood pressure. I’ve never experienced this to this degree during my pregnancies. Is this normal? Does it have to do with my varicosities/compression panty hose? I’m finally laying down to go to sleep with an ice pack on my shin - I hope to feel better soon! I’ve also had lots of strong BH’s all night- but have drank so so much water I cannot imagine that it’s because I’m dehydrated. Any suggestions are welcomed!