What Causes Heartburn,excess Appetite And Nausea?

K I m confused I don t know if I m pregnant or just crazy I took 3 pregnantcy test and all negative but I have really bad heartburn for a week I m tired a lot more then normal I ve been eatting more then normal my clothes. Don t fit especially my bra I get nausea all day only throw up three times last week. My mood changes all the time