have you checked your form? here is a great link to show you how to bench.
are you fast? in other words can you lift explosively. do have a speed day for bench?
maybe you need to stop benching with a straight bar on a flat bench and use some variations. find a variation that you suck at the most. maybe use your weak point in the bench. you could try:
and any combination of those as well.
try putting some mass on weak links and then getting those links stronger with that extra mass. if you are not sure what they are then work your traps, rhomboids, shoulders, and lats.
without knowing more information that is about as precise as i can get.