Fainting ?

Has anyone had a history of passing out while pregnant? I passed out Friday and ended up in the er (I’ve never passed out before) they ran test and found out I was dehydrated (I was really surprised i stay on top of my water) so they gave me fluids and all my other test came back normal but today I was driving and started feeling lightheaded and dizzy I made it home but I’m still feeling the same way so I’ve been laying down I have an appointment in the morning but this scares me . I’m wondering if my body is having a hard time absorbing water but idk . Has anyone else experienced this ?