Dizziness and fainting?

I’m 5 weeks pregnant today and this morning on the way to work (I take a public tramway) I suddenly got very hot and dizzy, and my vision went all white and blurry. I felt like I was going to faint but got off the tram and sat down and felt better within a few minutes.

My question is… did anyone else experience extreme dizziness/almost fainting during their first trimester? I felt perfectly fine before it happened, it just came on suddenly. I have my first prenatal appointment scheduled for Friday and I haven’t had any other concerning symptoms.