FEELING LIGHT HEADED.. HELP?!?

THE LAST WEEK OR SO I HAVE BEEN GETTING VERY LIGHT HEADED AFTER AND BEFORE I EAT.. BUT IF I EAT SOMETHING EXPECIALLY WITH SUGAR IN IT GOES AND THEN COMES BACK LIKE HALF HOUR LATER AND ALSO MY APITITE AND GONE RIGHT DOWN. ALOT OF FOODS I USE TO LIKE MAKES ME FEEL SICK NOW WHEN I THINK ABOUT IT.. SUCH AS CHICKEN, POTATOES ETC.. CAN ANYONE HELP OR KNOW WHAT IT IS??