Almost passed out in Walmart

Anyone else almost pass out just from standing? I had walked around the store twice and felt fine. Was standing waiting for my pictures to be ready and I started to feel super warm. Then I started feeling lightheaded, my ears popped and I started getting disoriented. I’ decided to leave to get some fresh air, and was bumping into things with my cart, like something just wasn’t right. Half way out of the store I started to feel more normal, once in the fresh air I felt much better. But really freaked me out, I’m 16+5, 3rd pregnancy and it never has happened before. I’m going to let my doctor know tomorrow but wondering if anyone else experienced this