Dizziness?

Its one day before my period is supposed to start. We have been actively trying to conceive for about a month now. 
​This morning at work, I started having dizzy spells left and right. It didn't matter if I was sitting or standing. I ate a large lunch assuming it had something to do with possibly having a low blood sugar but the dizziness has continued on well into the night. 
​My question is has anyone experienced dizziness before they were supposed to start or when they first got pregnant? Any insight is helpful!