My knowledge is that if your body isn't ready to into labour, no matter what natural induction method you try - it just won't work. So yes, breastfeeding can bring on contractions in late gestation - but only if you're ready. If it seriously induced labour at this stage of pregnancy then chances are something may have gone wrong anyway.

As for you DD1 - feeding more is likely to do with your supply waning, as it does during pregnancy. Just go with the flow if you do want to keep feeding her and head towards tandem feeding, etc.

Someone might be able to help you with a better answer but this is my basic knowledge .