Its the blood flow .. The baby is taking a lot of blood so you haven't got as much blood flow ... But watch blood pressure and sugar levels as well and drink loads of water a day
I fainted twice before , once in the shower I tried to get out to sit down but I had soap running down my face and I fell , then I walked out about to go text my boyfriend what happened I fainted again it got all black and fuzzy but both times I landed on my butt and the baby is fine and healthy it's a scary thing
I was so weak in my first trimester and one day after a clinic visit, while walking home i fainted. I sat down for a while then i walked on. I had lost a lot of weight due to nausea because I wasn't able to keep much food down. After the first trimester i became strong again!
I'm only 9 weeks and had this experience in my first pregnancy but not this early during pregnancy and never that strong came very close to fainting