I've been exclusively breastfeeding, doing BLW/BLS and DD is now 8.5 months old and we wanting to start TTC. (so I was hoping for opposite information in here hehe)
I think each person is different, but if you really don't want to fall pregnant look at using either a condom or a diaphragm (note diaphragms are less effective, but I find they don't really 'ruin the mood' as much cos you can put them in a couple of hours before hand and take them out the next day). But they say its 95% effective if you are feeding every 3 hours (or less) exclusively, and you don't have your period back (there is also a rumour about having to do feeds overnight).