Pregnancy or Something Else?

Cherish

I really don't want to be pregnant but people keep saying I might be. It's strange because my boobs were hurting really badly a week before my period. They stopped hurting during my period. Then ever since my period ended (six days ago) I've been experiencing horrible headaches and nausea. I get really hungry, but when I eat something I get nauseated all over again. I took a pregnancy test 4 days ago and it was negative. The symptoms keep persisting though. I've read a lot about vaginal bleeding being mistaken for a period. My flow was pretty heavy and lasted for five days, a pretty normal period for me...

What is going on?