I had the same thing happen when I was 8 weeks pregnant, and it ended up being a tubal pregnancy. I wouldn't take the risk of your health, definitely go to the Dr.
You should really get checked out by a doctor if you don't have insurance maybe you can find a clinic for women like a plan parent hood or somewhere like that they will do pregnancy test for free.
Brown spotting is just old blood. If you still haven't got your period try taking another test.