4-5 weeks pregnant... I passed a blood clot...

It is normal to pass blood clots during pregnancy, however, if you are now testing negative on a pregnancy test it means that you have had a miscarriage. Did your doctor not explain this to you? They should have also done a transvaginal ultrasound to make sure that you have passed all of the gestational tissue because if you have not, you could have serious problems. Chances are, if you are testing negative, you have passed all of the residual products of conception, but you should make sure.