Feeling Unwell

Is disorientation and/or a dizzy feeling normal on your period? Is it just caused by the pain or something else? For the whole of today I've had trouble focusing on anything, my eyes just won't stay fixed for very long. Like I'm constantly looking around. I also feel really heavy, drowsy and slightly dizzy. As if I have vertigo almost. And my cramps have been the worst they've ever been even though my flow is pretty light.