I've had this with two pregnancies, it's awful. Mine was benign positional vertigo, and apparently the bit in the brain that deals with balance is right next to the but that deals with nausea - hence why some women get it in pregnancy.
There are really safe drugs you can take to help, and also some exercises you can do at home. Can't remember the name but should come up on google.
I'd see your GP tbh as they are best to advise, but yeah, it can be a crappy pregnancy thing
Drink more water, lots of it. Your body needs loads of fluid in pregnancy. Your amount of blood in your body increases by a third, you're sustaining another life (babies are 75% water), amniotic fluid, it's all water based.
Dizziness in pregnancy is often caused by having low blood pressure (less blood volume) and needs to be topped up constantly with fluid.
I had that too in the first trimester. It was due to my blood pressure dropping (which is normal in pregnancy) and my body adjusting to having much lower blood pressure. I was reassured it was nothing to worry about. Yours is probably nothing at all to worry about either, but nonetheless you should speak to the midwife if only to put your mind at ease.