When I had DD my period came back when she was about 3 months (I was exclusively breastfeeding but also using a dummy) and then they disappeared for a few months after that. It wasn't until she was about . . . well, somewhere between 9 and 12 months that they became regular and even now they still jerk me around by a few days each month! Perhaps wait another 7 days and take another test, if it's still BFN then you're probably not pregnant. If you're 10 days after your period is due (and therefore, theoretically 24 days post-ovulation) then a test at this time should be accurate but since you're breastfeeding, it's possible that you ovulated late in your cycle. HTH.