Passing out

I’m 13weeks today, and I passed out at my sister’s house. Thankfully I didn’t leave when I did, because I passed out 5mins after I said I needed to leave, she keep talking so I didn’t leave yet. Which I’m lucky I didn’t pass out while driving.. I did fell on my butt and didn’t hit my head. I have a doctors appointment tomorrow so they are gonna do ultrasound to make sure everything is okay. Ugh my lower back hurts and I feel exhausted: anyone else passed out in pregnancy before