ttc while breastfeeding

my son is 7mo he has started solids and bf 3-5 times during the day and 2-3 times during the night . my periods returned when he was about a month but have been way heavier and very irregular . i’ve taken opk but not consistently so i’ve only seen the test line same color or lighter than control line so not quite ovulating . how long did it take you to conceive while ebf?