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You can express breast milk (either manually or by using a breast pump) and give that milk to the baby using a spoon. But the reason for avoiding breastfeeding needs to be evaluated. Nose block is a common cause for refusal to feed. If the child is having a nose block, you can use Nasoclear drops two drops prior to each feed.
You have mentioned the baby's current weight as 6 lbs, for a three months old baby 6 lbs fall much below the normal range. Was the child preterm? How much was the birth weight?