My doctor just recently told me breastfeeding is about 70% effective at preventing pregnancy. So by breastfeeding you are having that 70% working against you if you’re trying to conceive but it’s still that 30% window for pregnancy. Also by you not having your period yet it’s going to be really hard to tell when there’s a possible chance of ovulation.
Breastfeeding can make it significantly harder to get pregnant. Not impossible though. The home tests will show if the hormone levels are at a minimum level so if you’re looking for more sensitivity for the test use traditional line ones. I was about to get referred for fertility treatments as well before having a positive pregnancy test the same cycle I finally had a positive ovulation test for the first time since I started using them about a year prior. I still haven’t ovulated (that I know of) at 3 months PP
Breastfeeding can cause ovulation to be delayed, so you may not be able to conceive while breastfeeding.