These few days I have been very sick. As in nauseated and vomiting just about all day (unless I'm sleep). I can't keep anything down (no food and not even liquids). My back hurts, breast are kind of sore but I have had my period, which was normal, for this month. What could be wrong with me besides pregnancy?

Countless conditions. Anything from a stomach virus that will run it's course (usually in about 3 days if you take clear liquids only) to something serious. You are just going to have to go be seen in person.