I need help!!

i had unprotected sex, I then took the levonelle (morning after pill). I was then roughly 2 weeks late on my period. Since then I've missed 3/4 periods but when I have had a period it is very light brown. I have taken several pregnancy tests and ALL negative. I am getting severe headache, lower abdominal pain, tenderness breast and feeling sick (been sick once with watery mucus). What should I do??

ive been to the doctors and they have sent me for blood tests but want to check for diabetes?