Help!

Kayla

So, my period is 13 days late but i took a pregnancy test today and it was negative, unfortunately. But something is definitely wrong. I've been having cramps and some of the time it feels like just some sore muscles in my lower abdominal region and other times, it feels like period cramps. I

have gotten brown discharge on two occasions in the last twoish weeks and I've been extremely nauseous. Could I still be pregnant or is it something else?