I'm having a similar thing going on. I heard from many sources that spotting (without heavy bleeding or cramping) is normal in the first trimester. Best bet is to get checked out by your doctor or at least talk to him/her. Are you feeling any pregnancy symptoms? I'm 5 weeks 2 days and I had on and off implantation spotting for several days, then the pinkish and brownish spotting started a couple days after I was late for my period. Now the spotting just seems to come back very briefly after I strain to go potty (sorry, tmi!!! Lol). I've got an appointment this Friday. I drove myself crazy worrying too and did tons of research. Then I talked to a friend of mine and she had spotting for the first 9 weeks of her pregnancy and carried to full term.... Good luck!!!
You need to call your Dr or go to the emergency room! This does not sound normal