When I was TTC my second I was still BF DS. I had AF back but the LP was all wonky from the feeding. I ended up using Vitex to help regulate my cycle. I don't know if I would do that with such a young bub though because it can dry up the milk supply. My DS was older (over a year) and I wasn't too fussed if he stopped.
This time round I was still BF, had the wonky LP again and thought I was reasonably safe. Then I cut out night feeds and a month later was staring at an unexpected BFP.
Apparently the BF method of contraception isn't as reliable if you are not feeding overnight.