I got pregnant with my 3rd while I was breastfeeding and on the minipill. I was only 7 weeks along when I found out (I never had a period after the birth of my 2nd, but I was throwing up for several days - big tip off for me). They are 18 months apart.
I got pregnant when my dd was 5 mos old. I was bf and not on any birth control. I found out at 8 weeks because of all the symptoms. My 2 oldest are 14 mos apart. They are basically like twins now at 6 and 5 years old, lol and best buddies as well.