When I fell pg the second time I was breastfeeding and found out I was 8 weeks pregnant, when I counted back from the dating scan it put ovulation at about cd48 so it is definitely possible! Probably more possible when breastfeeding. I remember feeling really tired and nauseous and went to the dr's who said could you be pregnant?! Was a huge surprise! I also remember having that heavy feeling in the lower abdomen and also could feel the uterus contract more when breastfeeding. Hope you get some clear answers soon, must be very frustrating not knowing definitely either way.