You have feed on one breast completely ( 20-25 min) , and then if he demands more feed , the other breast should be offered. If you change breast frequently while feeding , you give only foremilk which will quinch only thirst, baby will be hungry again. Since he is only 6 weeks, he should adjust to the sleep pattern.

Baby's usually sleep for around 2 hrs, if they have been adequately fed. Kindly check ur feed technique. Make sure there's a good latch. Also, kindly provide details of the current weight and the birth weight