Fi, have you read the BellyBelly article, 'Your Period and Ovulation After Baby?'

You breastfeeding wouldn't have contributed to your miscarriage, but I would say the gastro did. When we start to become fertile again after a baby and through breastfeeding, our body takes time to build up our good old hormones; first we have enough hormone to be able to ovulate. Then we have enough hormone to ovulate and conceive; then we have enough hormone to ovulate, conceive and sustain the pregnancy. The thresholds for each woman are unique so the time it takes to do this is unique.

Enjoy breastfeeding your gorgeous girl and don't let it stress you - she obviosly sees her boobies as being important to her right now so it's okay to give this to her. You're doing a great job!!!