So I had my period about 14 days ago and it was a few days late but was like a normal period when it did start. Yesterday I started to have a period like discharge but it was mostly dark brown. I'm a little concerned as I'm on the pill and have been very regular. But I've also been nausea for the past 2-3 days. I've thrown up just a little twice, but I also haven't been eating much. I am 22 years old and I sometimes use condoms while having sex. Also just took a pregnancy test and came out negative. What could this be?