In Galatians 6:2, the word for "burdens" is baros which means "heaviness, weight, burden, trouble". \
In Galatians 6:5, the word for load is "phortion" and means "of burdensome rites."
The first verse is speaking of helping one another through troubles and the second is speaking of the responsibility each person has in those troubles and sins.
There are certain Christian responsibilities or burdens each believer must bear which cannot be shared with others. Jesus assured His disciples that such burdens were light.