How to po kaya??

How to strengten my babies neck po kaya mga momsh??I feel like his neck is still weak pero kapag nasa tummy ko naman cia kaya niya ibangon ung ulo nya ng ilang minutes pero kapag kakargahin ko ramdam ko na parang newborn pa din cia malambot ung sa leeg nya at parang may mga buto na nagclicking sounds..Is it normal??BTW ,my baby is 2 1/2 months..I hope may makasagot..Thank you..