I fell pregnant while breastfeeding. We were (and still are) on 2 feeds through the day and one overnight around 3 am. DS was 18 months when I conceived. I'd literally only just had AF back once, and I'd just cut one feed through the day.
DS still wants the boob, and like Soon2be4, found around 14 months DS suddenly increased his boob demands (I started a thread on it because it was exhausting and I was so confused). I had to be very firm in maintaining boundaries around feeds.