Fell twice... Any ideas why?

Brittany
I went to a graduation ceremony last night, and I never noticed it before but apparently my family said its been happening for a while. 
I noticed at first, the more weight I'd put on my left leg, the more it would shake. Then, soon after I noticed that, I got dizzy and felt as if I was drunk; and then I fell over! 
At first, I waived it off as nothing, but then not even an hour later, it happened again! Needless to say, I got off my feet because last thing I want is to fall ON someone or get hurt. 
But, has this happened to anyone else? What did your doctor tell you to do? Should I call in at work?