Spotting at five weeks?

My husband and I have been trying for a baby for a few months now...This month, my period was late, I am extremely exhausted, and moody, my abdomen is bloated, and my montgomery glands are enlarged, and I have had cramping in my lower abdomen (all pregnancy symptoms to me)....today is day 38 in my cycle. I took a pregnancy test thins morning, and it was negative.? and now I have been having some reddish/brownish spotting? could I still be pregnant? Has this happened to anyone else?