My period was due on 17 feb I went for pregnancy test and it had been negative and this morning I had brown discharge

Did you take one at a doctor's office? If not, I'd go therer and I'd take another one in two weeks just to be sure. My best friend had the same thing happen to her with an at home test. It said she wasn't pregnant and she actually was.

Even if you're not pregnant, you should get a GYN checkup to make sure everything is OK.

Hope this helps ;-)