My newborn/infant can't seem to suck right on his pacifier?

My son is now 3 months old and he cant seem to keep a binky in his mouth. He doesn't seem to be able to keep a good suction on it. We have to hold it in his mouth for him. He loves his binky but cant keep it in. His mouth is fine and has no pallet problems or anything, he just cant seem to keep a bink in hs mouth. Whats wrong? We have bought and tried every kind of pacifier they make, but no luck. The best out of all are made by gerber, but r not the ortho kinds hey are just straight out with a circle base. Still we have to hold it in his mouth for him. Anyone else have this problem? My first son could suck on his bink and keep it in his mouth since he was 3 days old. My new baby is 3 months old and cant keep it in. Whats wrong?