gripewater

so my baby is 21 days old today and having some tough time pooping... he poop once in 12 hrs and get uncomfortable due to it.... i exclusively BF,,, i showed him to the doctors and everything is fine and they say if hes getting fussy because not pooping it doesnt matter but i get extremely concerned seeing my baby curling up and crying.... my mom told me to give him gripewater as she has given me and my sisters when we were babies but my gp says that they dont recommend gripewater to anyone here in Ireland ,,, what shall i do shall i give it or not?