baby feeding

hey,
we have 5 months old baby girl. till to now i was exclusively breastfeeding but from last week milk supply decreases and there is not enough milk for the baby. the problem is that my baby is rejecting formula feeding. what should i do
we have 5 months old baby girl. till to now i was exclusively breastfeeding but from last week milk supply decreases and there is not enough milk for the baby. the problem is that my baby is rejecting formula feeding. what should i do