Dear Craigy,  Just a thought: have you been on antibiotics recently?  Same thing happened to my baby when he was 6 weeks and it coincided  with a bout of oral thrush which had reached his digestive system.  The nappy pail reeked of yeast even when it only contained wet nappies. Thrush  also makes babies very windy.  A course of anti-fungal oral gel (prescribed by GP) and probiotics (self-  help remedy!) eventually got rid of the candida infection and he has been  filling his nappy more often and regularly though still only once a day (is now  16 weeks).  I only mention this because thrush in babies is not really taken seriously by docs  as it's not harmful, so it's easily missed. Prob a good idea to check with a breastfeeding counsellor  at a baby cafe? Infrequent bowel movements not generally regarded as a symptom  of thrush but I saw lots of Internet discussions where it was a common thing with babies who had it.  Don't want to alarm you cos it's not serious but it is a bore if left untreated...  Hope this helps    as it's not harmful