panda, please do not worry. bf-ing bbies rarely have problems poo-ing. some may poo as frequent as every feed.
at 5wks baby poo SHOULD be watery - usually yellow, sometimes green. in fact, soft poo is the ideal poo. what you DO NOT want is solid poo, which probably means baby is constipated.
please DO NOT stop breastfeeding if you have good milk supply. breastmilk is the BEST food for baby - it has just the right nutrients. it is so perfect that to date, no scientist or nutritionist or pediatrician or doctor has been able to replicate it 100%. that is why the fm tins always have a disclaimer that says "breastmilk is still best for baby".
also, feeding straight from breast helps maintain & increase your milk supply. it's also wonderful bonding for mummy & baby.
it helps to do a little reading or surfing to find out more about newborn baby care, esp in the first 3 months. will help answer loads of questions & clear your doubts.