Dealing with recurrent fainting & low blood pressure

Well I fainted at work this morning, third time this pregnancy and I'm only 18 weeks. I eat good breakfast everyday. Today I blacked out for almost 10minutes and my blood pressure was 60/40. Dr said to just drink more water and lay down when it's about to happen. Anyone else dealing with this? Idk how to go 5 more months worrying I may pass out at any moment or while driving. Husband is very concerned but I've heard it's common.