true constipation is usually hard balls. Many BF babes go days and days starting at about 4 months old - but two weeks? I would say every 3 days might fine as long as his weight gain is ok. But many babes poop every feeding at that age and slow down later on.
The day of the big event might be a little gassy...massage, leg bicycling, etc. might help, sometimes I used fennel tea for gassiness. When they do go it's often thicker and darker and smellier than you're used to - but constipation is more like rabbit pellets. Peds sometime suggest interventions, but that's becuase formula fed babes so often get constipated. it's possible, but quite rare in BF babe. Frequency is not what you should use to judge whether or not a babe is constipated. (despite what some of those strange colon cleansing people say about daily bowel movements...infant of this age very often do not and are in perfect bowel health - interventions disrupt how efficiently their intestines are processing BM...with little waste.