It is completely normal and healthy for an infant to prefer their mother, as you are their 'safe space.' Breastfeeding does not prevent a baby from forming a bond with a nanny or other caregivers; that bond develops through time spent together. Even if your baby fusses when you are present, they are often perfectly happy and content when you are not there. Continue to breastfeed if you wish, as the benefits far outweigh any temporary adjustment period with a caregiver.