I breastfed for 18 months, did not have a period in that time and did not conceive during that time either. But it is possible to conceive during the breastfeeding phase, all that has to happen is that your hormones for ovulation have to be stronger than the prolactin that causes the breast milk. One ovulates, one can get pregnant.
BFP means big fat positive with a pregnancy test. as for the breastfeeding i dont know much about it sorry xo