Extreme nausea during period?

For the past 5 days I have had very light spotting and no cramps. I assume it's just my period taking a while to start, as it was due yesterday. The past 2 days I have been very nauseous and even threw up last night. I'm not one to ever throw up, so this is really strange for me. I did take a hpt this morning and it was negative. Has anyone else experienced this? Its awful!