2 Days Ago I Went To The Doctor Thinking I

2 days ago I went to the doctor thinking I had the flu. My test came back negative but she said it May be to early to tell. Now I'm having terrible migraines that are keeping me up at night and pain releavers aren't helping, im also having a eatery green diarrhea. How can I be sure this isn't something more than the flu and what can I do about my headaches?