Got really dizzy at work.

So I am a cashier at work (plus 13 week pregnant) and today I was only working a 4 hour shift but I got so dizzy today at work for the first time (and it happened twice within a 3 hour time) ever and I almost passed out but got someone to cover me and sat down for a couple minutes. What could help with this if it happens again. I am horrible with drinking water but I try. Lately water just gets me sick really anything I drink gets me sick. Any ideas of what could help me?