I had brown spotting with my first pregnancy, at about 7 weeks. I gave birth to a beautiful, perfectly healthy girl. My OB, at the time, told me that they don't worry over dark blood. Probably just implantation bleeding, but definitely check with your OB in case!
-1st
I have heard any spotting that is NOT red or pink is ok. Brown blood means old blood. I would call your doctor just to be sure, but I bet you're just fine! :) I know how worrisome it can be. I had brown spotting this morning (more like brown tinged CM) but I also had a pap done yesterday so I know it was from that. Hang in there and keep us posted!