Ite sounds like your light bleeding could have been implantation bleeding. Unless you know for a fact you ovulated. Either way, wait till your missed period. you could get a negative until 6 weeks sometimes. Or take one now and test again in a week. Always wait 3 days at least to allow hcg to go up. Good luck.
Similar thing happened to me.. I tested negative at the Dr's for about three to four weeks.. Missed my period again and tested positive. You can take it now.. But my dr said it takes two weeks from conception to produce enough HCG hormon to test positive