My baby is suddenly refusing to nurse. Does this mean he's weaning?

Very unlikely. Occasionally, a baby who has been nursing well will suddenly refuse the breast for no apparent reason.  This is called a nursing strike.  It is very rare that a baby will wean on his own during his first year, and weaning usually happens gradually. On reviewing the situation, a cause for the nursing strike can sometimes be identified. Common causes include: an earache or stuffy nose, a scary sound that happened while breastfeeding, a different lotion or deodorant, too many bottles or pacifiers or a recent change in routine. Nursing strikes can last from 2-4 days.