Light headed/fainting

Has anyone else been having light headed near fainting spells? I had them with my first but not until a little later (I’m 18weeks now). Today I was so close to passing out (I felt it coming on for a little- I was standing in a long line) I knelt down for a few and then stood up slowly again and my vision completely started to go like I was about to pass out so I quickly sat down again and put my head forward- after it passed I was fine a little off but better. Today I’ve felt slightly light headed.

My blood pressure is already on the low side (I’m usually anywhere between 90/60-100/70) a few weeks ago when I was sick I was 100/50 but my appointment on Friday I was 100/60. In almost positive these are from drops in BP throughout the day but wondering if anyone else is experiencing them too? I’m trying to up my water intake and slow down a bit. I’ve been so nauseous so eating has really been slacking which I’m sure is just not helping.