Advice please

So for the past two months of my pregnancy I go threw funny spells, i get hot, I go all dizzy , my ears ring , my legs go weak and my vision goes blurry or sometimes even white so I can't see anything and once it's past I get severe cramps!

I've been to the doctor and I've had my blood pressure checked , blood work and pee tests and it's all come back clear, but today it happened(I haven't been feeling great for about a week very weak and sick so I didn't go to work today) but I thought I'd just go stand out side and get some fresh air and it happened as I was trying to make my way back to the sofa I head butted a wall my doctor told me last time to call if it happened again but by the time the episode had finished the doctors was closed, I'm still not feeling 100% and still feel really dizzy and sick and I just don't know what to do any help?