light headed & dizzy.. still

I’m still feeding light headed & dizzy as I have been the past 3 days.. I’ve taken two pregnancy tests that were both negative. My period ended Monday. I tried to contact my doctor and the nurse said as long as I am eating and drinking, she is not concerned. I can’t even sit down without feeling like I am going to pass out. The nurse said I can go to Urgent Care or the hospital. Has anybody ever had this? It’s constant and it will not go away. Nothing makes it go away. Please read previous post if further questioning! Thanks :(