For a while I got this, really really bad - on my first day of my period I'd get nausea, dizziness, would pretty much throw up if I ate anything. It really freaked me out, because my actual periods were no different, and I'd always had fairly light, pain-free periods. The first time it happened I was out with my boyfriend and ended up vomiting all over a park bench, I thought I had a stomach bug but then it happened a few more times and I realised the correlation :L
Sionce then I went on the pill (not for that reason though) so my periods have stopped and obviously it doens't happen anymore, I never really worked out a cure for it though other than that =/ So yeah, go to your GP and maybe they can suggest something?