Hello there. What you are experiencing is called lactational amenorrhoea. It's a normal phenomenon while breastfeeding because breast feeding delays the normal ovarian cycles by disrupting the pattern and rhythmic release of certain hormones which otherwise occur when you are not in the post partum face of feeding. There has been studies and it has been observed that there is a strong relationship between the amount of suckling and the contraceptive effect of lactational amenorrhoea. Normal menstrual cycles can start anywhere between 8-14 months. It's perfectly normal and no side effects are being caused. In fact it's a excellent time to lose those few extra pounds by breast feeding. And you don't have to even use any contraceptive method during this phase. Consult a gynaecologist for further help. Regards