Confused! Help?!?!?

So my fiance and I had intercourse and then my period was 6 days late!!!! It's always on time or a day after, but never 6 days. So I took a pregnancy test and it was a BFN I started to bleed on the 7th day, but it was really unusual it was WAY lighter and no cramps (I usually have major cramps) it comes on and off it goes from red to pink an a few times brown. What's going on? HELP!!!!!