Idk whats wrong I've been feeling nauseous and dizzy for almost 3 weeks ...I vomited once before my…

Idk whats wrong I've been feeling nauseous and dizzy for almost 3 weeks ...I vomited once before my period started which was shorter than usual and came 2 days early ... the sick feeling hasn't went away but negative pregnancy test .. I'm going to make a doctor appointment Monday but does anyone have any ideas