Help!

My S/O and I have been trying for a month so far to get pregnant. My period was supposed to come October 28 but it was late. Naturally, I thought I was pregnant but now I'm not so sure. I took a test the other night and it came back negative. I read that negative results could be false because I took the test later at night and because I had a soda right before I took the test. Today, November 10, I thought I started my period but it wasn't normal. It was a dark brownish color. Could I still be pregnant? What should I do?