Worried

I'm 6w along and I just feel off. My headaches are horrible, and when I eat I can only take a couple bites before I get full. I only ate 3 times today but it was hardly anything. 1/2 bagel, soup, and an enchilada. I see my doctor on Friday... Just stressed... Any advice? 
Btw this is my 3rd child... I never had this happen before with previous pregnancies